keytool - Key and Certificate Management Tool

Manages a keystore (database) of private keys and their associated X.509 certificate chains authenticating the corresponding public keys. Also manages certificates from trusted entities.

SYNOPSIS

keytool [ commands ]

DESCRIPTION

keytool is a key and certificate management utility. It enables users to administer their own public/private key pairs and associated certificates for use in self-authentication (where the user authenticates himself/herself to other users/services) or data integrity and authentication services, using digital signatures. It also allows users to cache the public keys (in the form of certificates) of their communicating peers.

A certificate is a digitally signed statement from one entity, saying that the public key (and some other information) of some other entity has a particular value. (See Certificates.) When data is digitally signed, the signature can be verified to check the data integrity and authenticity. Integrity means that the data has not been modified or tampered with, and authenticity means the data indeed comes from whoever claims to have created and signed it.

keytool stores the keys and certificates in a so-called keystore. The default keystore implementation implements the keystore as a file. It protects private keys with a password.

The jarsigner tool uses information from a keystore to generate or verify digital signatures for Java ARchive (JAR) files. (A JAR file packages class files, images, sounds, and/or other digital data in a single file). jarsigner verifies the digital signature of a JAR file, using the certificate that comes with it (it is included in the signature block file of the JAR file), and then checks whether or not the public key of that certificate is "trusted", i.e., is contained in the specified keystore.

Please note: the keytool and jarsigner tools completely replace the javakey tool provided in JDK 1.1. These new tools provide more features than javakey, including the ability to protect the keystore and private keys with passwords, and the ability to verify signatures in addition to generating them. The new keystore architecture replaces the identity database that javakey created and managed. It is possible to import the information from an identity database into a keystore, via the -identitydb keytool command.

Keystore Entries

There are two different types of entries in a keystore:
  1. key entries - each holds very sensitive cryptographic key information, which is stored in a protected format to prevent unauthorized access. Typically, a key stored in this type of entry is a secret key, or a private key accompanied by the certificate "chain" for the corresponding public key. The keytool and jarsigner tools only handle the latter type of entry, that is private keys and their associated certificate chains.

  2. trusted certificate entries - each contains a single public key certificate belonging to another party It is called a "trusted certificate" because the keystore owner trusts that the public key in the certificate indeed belongs to the identity identified by the "subject" (owner) of the certificate. The issuer of the certificate vouches for this, by signing the certificate.

Keystore Aliases

All keystore entries (key and trusted certificate entries) are accessed via unique aliases. Aliases are case-insensitive; the aliases Hugo and hugo would refer to the same keystore entry.

An alias is specified when you add an entity to the keystore using the -genkey command to generate a key pair (public and private key) or the -import command to add a certificate or certificate chain to the list of trusted certificates. Subsequent keytool commands must use this same alias to refer to the entity.

For example, suppose you use the alias duke to generate a new public/private key pair and wrap the public key into a self-signed certificate via the following command: 

    keytool -genkey -alias duke -keypass dukekeypasswd
This specifies an inital password of "dukekeypasswd" required by subsequent commands to access the private key assocated with the alias duke. If you later want to change duke's private key password, you would use a command like the following: 
    keytool -keypasswd -alias duke -keypass dukekeypasswd -new newpass
This changes the password from "dukekeypasswd" to "newpass".

Please note: A password should not actually be specified on a command line or in a script unless it is for testing purposes, or you are on a secure system. If you don't specify a required password option on a command line, you will be prompted for it. When typing in a password at the password prompt, the password is currently echoed (displayed exactly as typed), so be careful not to type it in front of anyone.

Keystore Location

Each keytool command has a -keystore option for specifying the name and location of the persistent keystore file for the keystore managed by keytool. The keystore is by default stored in a file named .keystore in the user's home directory, as determined by the "user.home" system property. On Solaris systems "user.home" defaults to the user's home directory.

Keystore Creation

A keystore is created whenever you use a -genkey, -import, or -identitydb command to add data to a keystore that doesn't yet exist.

More specifically, if you specify, in the -keystore option, a keystore that doesn't yet exist, that keystore will be created.

If you don't specify a -keystore option, the default keystore is a file named .keystore in your home directory. If that file does not yet exist, it will be created.

Keystore Implementation

The KeyStore class provided in the java.security package supplies well-defined interfaces to access and modify the information in a keystore. It is possible for there to be multiple different concrete implementations, where each implementation is that for a particular type of keystore.

Currently, there are two command-line tools that make use of keystore implementations (keytool and jarsigner), and also a GUI-based tool named policytool. Since KeyStore is publicly available, JDK users can write additional security applications that use it.

There is a built-in default implementation, provided by Sun Microsystems. It implements the keystore as a file, utilizing a proprietary keystore type (format) named "JKS". It protects each private key with its individual password, and also protects the integrity of the entire keystore with a (possibly different) password.

Keystore implementations are provider-based. More specifically, the application interfaces supplied by KeyStore are implemented in terms of a "Service Provider Interface" (SPI). That is, there is a corresponding abstract KeystoreSpi class, also in the java.security package, which defines the Service Provider Interface methods that "providers" must implement. (The term "provider" refers to a package or a set of packages that supply a concrete implementation of a subset of services that can be accessed by the Java Security API.) Thus, to provide a keystore implementation, clients must implement a "provider" and supply a KeystoreSpi subclass implementation, as described in How to Implement a Provider for the Java Cryptography Architecture.

Applications can choose different types of keystore implementations from different providers, using the "getInstance" factory method supplied in the KeyStore class. A keystore type defines the storage and data format of the keystore information, and the algorithms used to protect private keys in the keystore and the integrity of the keystore itself. Keystore implementations of different types are not compatible.

keytool works on any file-based keystore implementation. (It treats the keytore location that is passed to it at the command line as a filename and converts it to a FileInputStream, from which it loads the keystore information.) The jarsigner and policytool tools, on the other hand, can read a keystore from any location that can be specified using a URL.

The tools currently choose a keystore implementation based simply on the value of the keystore.type property specified in the security properties file. The security properties file is called java.security, and it resides in the JDK security properties directory, java.home/lib/security, where java.home is the JDK installation directory.

Each tool gets the keystore.type value and then examines all the currently-installed providers until it finds one that implements keystores of that type. It then uses the keystore implementation from that provider.

The KeyStore class defines a static method named getDefaultType that lets applications and applets retrieve the value of the keystore.type property. The following line of code creates an instance of the default keystore type (as specified in the keystore.type property): 

    KeyStore keyStore = KeyStore.getInstance(KeyStore.getDefaultType());

The default keystore type is "jks" (the proprietary type of the keystore implementation provided by Sun). This is specified by the following line in the security properties file: 

    keystore.type=jks

To have the tools utilize a keystore implementation other than the default, you can change that line to specify a different keystore type.

For example, if you have a provider package that supplies a keystore implementation for a keystore type called "pkcs12", change the line to 

    keystore.type=pkcs12
Note: case doesn't matter in keystore type designations. For example, "JKS" would be considered the same as "jks".

Alternatively, for keytool, you can specify a keystore type at the command line, via the -storetype option; and for policytool, you can specify a keystore type via the "Change Keystore" command in the Edit menu.

Supported Algorithms and Key Sizes

keytool allows users to specify any key pair generation and signature algorithm supplied by any of the registered cryptographic service providers, i.e., the keyalg and sigalg options for various commands must be supported by a provider implementation. The default key pair generation algorithm is "DSA". The signature algorithm is derived from the algorithm of the underlying private key: If the underlying private key is of type "DSA", the default signature algorithm is "SHA1withDSA", and if the underlying private key is of type "RSA", the default signature algorithm is "MD5withRSA".

When generating a DSA key pair, the key size must be in the range from 512 to 1024 bits, and must be a multiple of 64. The default key size for any algorithm is 1024 bits.

Certificates

A certificate (also known as a public-key certificate) is a digitally signed statement from one entity (the issuer), saying that the public key (and some other information) of another entity (the subject) has some specific value.

Let us expand on some of the key terms used in this sentence:

Public Keys
These are numbers associated with a particular entity, and are intended to be known to everyone who needs to have trusted interactions with that entity. Public keys are used to verify signatures.
Digitally Signed
If some data is digitally signed it has been stored with the "identity" of an entity, and a signature that proves that entity knows about the data. The data is rendered unforgeable by signing with the entity's private key.
Identity
A known way of addressing an entity. In some systems the identity is the public key, in others it can be anything from a Unix UID to an Email address to an X.509 Distinguished Name.
Signature
A signature is computed over some data using the private key of an entity (the signer).
Private Keys
These are numbers, each of which is supposed to be known only to the particular entity whose private key it is (that is, it's supposed to be kept secret). Private and public keys exist in pairs in all public key cryptography systems (also referred to as "public key crypto systems"). In a typical public key crypto system, such as DSA, a private key corresponds to exactly one public key. Private keys are used to compute signatures.
Entity
An entity is a person, organization, program, computer, business, bank, or something else you are trusting to some degree.

Basically, public key cryptography requires access to users' public keys. In a large-scale networked environment it is impossible to guarantee that prior relationships between communicating entities have been established or that a trusted repository exists with all used public keys. Certificates were invented as a solution to this public key distribution problem. Now a Certification Authority (CA) can act as a Trusted Third Party. CAs are entities (e.g., businesses) that are trusted to sign (issue) certificates for other entities. It is assumed that CAs will only create valid and reliable certificates as they are bound by legal agreements. There are many public Certification Authorities, such as VeriSign, Thawte, Entrust, and so on. You can also run your own Certification Authority using products such as the Netscape/Microsoft Certificate Servers or the Entrust CA product for your organization.

Using keytool, it is possible to display, import, and export certificates. It is also possible to generate self-signed certificates.

keytool currently handles X.509 certificates.

X.509 Certificates

The X.509 standard defines what information can go into a certificate, and describes how to write it down (the data format). All X.509 certificates have the following data, in addition to the signature:
Version
This identifies which version of the X.509 standard applies to this certificate, which affects what information can be specified in it. Thus far, three versions are defined. keytool can import and export v1, v2, and v3 certificates. It generates v1 certificates.
Serial Number
The entity that created the certificate is responsible for assigning it a serial number to distinguish it from other certificates it issues. This information is used in numerous ways, for example when a certificate is revoked its serial number is placed in a Certificate Revocation List (CRL).
Signature Algorithm Identifier
This identifies the algorithm used by the CA to sign the certificate.
Issuer Name
The X.500 Distinguished Name of the entity that signed the certificate. This is normally a CA. Using this certificate implies trusting the entity that signed this certificate. (Note that in some cases, such as root or top-level CA certificates, the issuer signs its own certificate.)
Validity Period
Each certificate is valid only for a limited amount of time. This period is described by a start date and time and an end date and time, and can be as short as a few seconds or almost as long as a century. The validity period chosen depends on a number of factors, such as the strength of the private key used to sign the certificate or the amount one is willing to pay for a certificate. This is the expected period that entities can rely on the public value, if the associated private key has not been compromised.
Subject Name
The name of the entity whose public key the certificate identifies. This name uses the X.500 standard, so it is intended to be unique across the Internet. This is the X.500 Distinguished Name (DN) of the entity, for example, 
    CN=Java Duke, OU=Java Software Division, O=Sun Microsystems Inc, C=US
(These refer to the subject's Common Name, Organizational Unit, Organization, and Country.)
Subject Public Key Information
This is the public key of the entity being named, together with an algorithm identifier which specifies which public key crypto system this key belongs to and any associated key parameters.

X.509 Version 1 has been available since 1988, is widely deployed, and is the most generic.

X.509 Version 2 introduced the concept of subject and issuer unique identifiers to handle the possibility of reuse of subject and/or issuer names over time. Most certificate profile documents strongly recommend that names not be reused, and that certificates should not make use of unique identifiers. Version 2 certificates are not widely used.

X.509 Version 3 is the most recent (1996) and supports the notion of extensions, whereby anyone can define an extension and include it in the certificate. Some common extensions in use today are: KeyUsage (limits the use of the keys to particular purposes such as "signing-only") and AlternativeNames (allows other identities to also be associated with this public key, e.g. DNS names, Email addresses, IP addresses). Extensions can be marked critical to indicate that the extension should be checked and enforced/used. For example, if a certificate has the KeyUsage extension marked critical and set to "keyCertSign" then if this certificate is presented during SSL communication, it should be rejected, as the certificate extension indicates that the associated private key should only be used for signing certificates and not for SSL use.

All the data in a certificate is encoded using two related standards called ASN.1/DER. Abstract Syntax Notation 1 describes data. The Definite Encoding Rules describe a single way to store and transfer that data.

X.500 Distinguished Names

X.500 Distinguished Names are used to identify entities, such as those which are named by the subject and issuer (signer) fields of X.509 certificates. keytool supports the following subparts:
  • commonName - common name of a person, e.g., "Susan Jones"

  • organizationUnit - small organization (e.g, department or division) name, e.g., "Purchasing"

  • organizationName - large organization name, e.g., "ABCSystems, Inc."

  • localityName - locality (city) name, e.g., "Palo Alto"

  • stateName - state or province name, e.g., "California"

  • country - two-letter country code, e.g., "CH"

When supplying a distinguished name string as the value of a -dname option, as for the -genkey or -selfcert commands, the string must be in the following format: 

CN=cName, OU=orgUnit, O=org, L=city, S=state, C=countryCode

where all the italicized items represent actual values and the above keywords are abbreviations for the following: 

	CN=commonName
	OU=organizationUnit
	O=organizationName
	L=localityName
	S=stateName
	C=country

A sample distinguished name string is 

CN=Mark Smith, OU=JavaSoft, O=Sun, L=Cupertino, S=California, C=US
and a sample command using such a string is 
keytool -genkey -dname "CN=Mark Smith, OU=JavaSoft, O=Sun, L=Cupertino, 
S=California, C=US" -alias mark

Case does not matter for the keyword abbreviations. For example, "CN", "cn", and "Cn" are all treated the same.

Order matters; each subcomponent must appear in the designated order. However, it is not necessary to have all the subcomponents. You may use a subset, for example: 

CN=Steve Meier, OU=SunSoft, O=Sun, C=US

If a distinguished name string value contains a comma, it must be escaped by a "\" character, as in 

   cn=peter schuster, o=Sun Microsystems\, Inc., o=sun, c=us

It is never necessary to specify a distinguished name string on a command line. If it is needed for a command, but not supplied on the command line, the user is prompted for each of the subcomponents.

The Internet RFC 1421 Certificate Encoding Standard

Certificates are often stored using the printable encoding format defined by the Internet RFC 1421 standard, instead of their binary encoding. This certificate format, also known as "Base 64 encoding", facilitates exporting certificates to other applications by email or through some other mechanism.

Certificates read by the -import and -printcert commands can be in either this format or binary encoded.

The -export command by default outputs a certificate in binary encoding, but will instead output a certificate in the printable encoding format, if the -rfc option is specified.

The -list command by default prints the MD5 fingerprint of a certificate. If the -v option is specified, the certificate is printed in human-readable format, while if the -rfc option is specified, the certificate is output in the printable encoding format.

In its printable encoding format, the encoded certificate is bounded at the beginning by 

-----BEGIN CERTIFICATE-----

and at the end by 

-----END CERTIFICATE-----

Certificate Chains

keytool can create and manage keystore "key" entries that each contain a private key and an associated certificate "chain". The first certificate in the chain contains the public key corresponding to the private key.

When keys are first generated (see the -genkey command), the chain starts off containing a single element, a self-signed certificate. A self-signed certificate is one for which the issuer (signer) is the same as the subject (the entity whose public key is being authenticated by the certificate). Whenever the -genkey command is called to generate a new public/private key pair, it also wraps the public key into a self-signed certificate.

Later, after a Certificate Signing Request (CSR) has been generated (see the -certreq command) and sent to a Certification Authority (CA), the response from the CA is imported (see -import), and the self-signed certificate is replaced by a chain of certificates. At the bottom of the chain is the certificate (reply) issued by the CA authenticating the subject's public key. The next certificate in the chain is one that authenticates the CA's public key.

In many cases, this is a self-signed certificate (that is, a certificate from the CA authenticating its own public key) and the last certificate in the chain. In other cases, the CA may return a chain of certificates. In this case, the bottom certificate in the chain is the same (a certificate signed by the CA, authenticating the public key of the key entry), but the second certificate in the chain is a certificate signed by a different CA, authenticating the public key of the CA you sent the CSR to. Then, the next certificate in the chain will be a certificate authenticating the second CA's key, and so on, until a self-signed "root" certificate is reached. Each certificate in the chain (after the first) thus authenticates the public key of the signer of the previous certificate in the chain.

Many CAs only return the issued certificate, with no supporting chain, especially when there is a flat hierarchy (no intermediates CAs). In this case, the certificate chain must be established from trusted certificate information already stored in the keystore.

A different reply format (defined by the PKCS#7 standard) also includes the supporting certificate chain, in addition to the issued certificate. Both reply formats can be handled by keytool.

The top-level (root) CA certificate is self-signed. However, the trust into the root's public key does not come from the root certificate itself (anybody could generate a self-signed certificate with the distinguished name of say, the VeriSign root CA!), but from other sources like a newspaper. The root CA public key is widely known. The only reason it is stored in a certificate is because this is the format understood by most tools, so the certificate in this case is only used as a "vehicle" to transport the root CA's public key. Before you add the root CA certificate to your keystore, you should view it (using the -printcert option) and compare the displayed fingerprint with the well-known fingerprint (obtained from a newspaper, the root CA's webpage, etc.).

Importing Certificates

To import a certificate from a file, use the -import command, as in 

    keytool -import -alias joe -file jcertfile.cer

This sample command imports the certificate(s) in the file jcertfile.cer and stores it in the keystore entry identified by the alias joe.

You import a certificate for two reasons:

  1. to add it to the list of trusted certificates, or

  2. to import a certificate reply received from a CA as the result of submitting a Certificate Signing Request (see the -certreq command) to that CA.

Which type of import is intended is indicated by the value of the -alias option. If the alias exists in the database, and identifies an entry with a private key, then it is assumed you want to import a certificate reply. keytool checks whether the public key in the certificate reply matches the public key stored with the alias, and exits if they are different. If the alias identifies the other type of keystore entry, the certificate will not be imported. If the alias does not exist, then it will be created and associated with the imported certificate.

WARNING Re: Importing Trusted Certificates

IMPORTANT: Be sure to check a certificate very carefully before importing it as a trusted certificate!

View it first (using the -printcert command, or the -import command without the -noprompt option), and make sure that the displayed certificate fingerprint(s) match the expected ones. For example, suppose someone sends or emails you a certificate, and you put it in a file named /tmp/cert. Before you consider adding the certificate to your list of trusted certificates, execute a -printcert command to view its fingerprints, as in 

  keytool -printcert -file /tmp/cert
    Owner: CN=ll, OU=ll, O=ll, L=ll, S=ll, C=ll
    Issuer: CN=ll, OU=ll, O=ll, L=ll, S=ll, C=ll
    Serial Number: 59092b34
    Valid from: Thu Sep 25 18:01:13 PDT 1997 until: Wed Dec 24 17:01:13 PST 1997
    Certificate Fingerprints:
         MD5:  11:81:AD:92:C8:E5:0E:A2:01:2E:D4:7A:D7:5F:07:6F
         SHA1: 20:B6:17:FA:EF:E5:55:8A:D0:71:1F:E8:D6:9D:C0:37:13:0E:5E:FE
Then call or otherwise contact the person who sent the certificate, and compare the fingerprint(s) that you see with the ones that they show. Only if they are equal is it guaranteed that the certificate has not been replaced in transit with somebody else's (e.g., an attacker's) certificate. If such an attack took place, and you did not check the certificate before you imported it, you would end up trusting anything the attacker has signed (e.g., a JAR file with malicious class files inside).

Note: it is not required that you execute a -printcert command prior to importing a certificate, since before adding a certificate to the list of trusted certificates in the keystore, the -import command prints out the certificate information and prompts you to verify it. You then have the option of aborting the import operation. Note, however, this is only the case if you invoke the -import command without the -noprompt option. If the -noprompt option is given, there is no interaction with the user.

Exporting Certificates

To export a certificate to a file, use the -export command, as in 

    keytool -export -alias jane -file janecertfile.cer
This sample command exports jane's certificate to the file janecertfile.cer. That is, if jane is the alias for a key entry, the command exports the certificate at the bottom of the certificate chain in that keystore entry. This is the certificate that authenticates jane's public key.

If, instead, jane is the alias for a trusted certificate entry, then that trusted certificate is exported.

Displaying Certificates

To print out the contents of a keystore entry, use the -list command, as in 

    keytool -list -alias joe
If you don't specify an alias, as in 
    keytool -list
the contents of the entire keystore are printed.

To display the contents of a certificate stored in a file, use the -printcert command, as in 

    keytool -printcert -file certfile.cer

This displays information about the certificate stored in the file certfile.cer.

Note: This works independently of a keystore, i.e., you do not need a keystore in order to display a certificate that's stored in a file.

Generating a self-signed certificate

A self-signed certificate is one for which the issuer (signer) is the same as the subject (the entity whose public key is being authenticated by the certificate). Whenever the -genkey command is called to generate a new public/private key pair, it also wraps the public key into a self-signed certificate.

You may occasionally wish to generate a new self-signed certificate. For example, you may want to use the same key pair under a different identity (distinguished name). For example, suppose you change departments. You can then:

  1. copy (clone) the original key entry. See -keyclone.

  2. generate a new self-signed certificate for the cloned entry, using your new distinguished name. See below.

  3. generate a Certificate Signing Requests for the cloned entry, and import the reply certificate or certificate chain. See the -certreq and -import commands.

  4. delete the original (now obsolete) entry. See -delete.

To generate a self-signed certificate, use the -selfcert command, as in 
    keytool -selfcert -alias dukeNew -keypass b92kqmp
      -dname "cn=Duke Smith, ou=Purchasing, o=BlueSoft, c=US"
The generated certificate is stored as a single-element certificate chain in the keystore entry identified by the specified alias (in this case "dukeNew"), where it replaces the existing certificate chain.

COMMAND AND OPTION NOTES

The various commands and their options are listed and described below . Note:

Option Defaults

Below are the defaults for various option values. 
-alias "mykey"

-keyalg "DSA"

-keysize 1024

-validity 90

-keystore the file named .keystore in the user's home directory

-file stdin if reading, stdout if writing
The signature algorithm (-sigalg option) is derived from the algorithm of the underlying private key: If the underlying private key is of type "DSA", the -sigalg option defaults to "SHA1withDSA", and if the underlying private key is of type "RSA", -sigalg defaults to "MD5withRSA".

Options that Appear for Most Commands

The -v option can appear for all commands except -help. If it appears, it signifies "verbose" mode; detailed certificate information will be output.

There is also a -Jjavaoption option that may appear for any command. If it appears, the specified javaoption string is passed through directly to the Java interpreter. (keytool is actually a "wrapper" around the interpreter.) This option should not contain any spaces. It is useful for adjusting the execution environment or memory usage. For a list of possible interpreter options, type java -h or java -X at the command line.

There are three options that may appear for all commands operating on a keystore:

-storetype storetype
This qualifier specifies the type of keystore to be instantiated. The default keystore type is the one that is specified as the value of the "keystore.type" property in the security properties file, which is returned by the static getDefaultType method in java.security.KeyStore.

-keystore keystore
The keystore (database file) location. Defaults to the file .keystore in the user's home directory, as determined by the "user.home" system property. On Solaris systems "user.home" defaults to the user's home directory.

-storepass storepass
The password which is used to protect the integrity of the keystore.

storepass must be at least 6 characters long. It must be provided to all commands that modify the keystore contents. For such commands, if a -storepass option is not provided at the command line, the user is prompted for it.

When retrieving information from the keystore, the password is optional; if no password is given, the integrity of the retrieved information cannot be checked and a warning is displayed.

Be careful with passwords - see Warning Regarding Passwords.

Warning Regarding Passwords

Most commands operating on a keystore require the store password. Some commands require a private key password.

Passwords can be specified on the command line (in the -storepass and -keypass options, respectively). However, a password should not be specified on a command line or in a script unless it is for testing purposes, or you are on a secure system.

If you don't specify a required password option on a command line, you will be prompted for it. When typing in a password at the password prompt, the password is currently echoed (displayed exactly as typed), so be careful not to type it in front of anyone.

COMMANDS

See also the Command and Option Notes.

Adding Data to the Keystore

-genkey {-alias alias} {-keyalg keyalg} {-keysize keysize} {-sigalg sigalg} [-dname dname] [-keypass keypass] {-validity valDays} {-storetype storetype} {-keystore keystore} [-storepass storepass] {-v} {-Jjavaoption}

Generates a key pair (a public key and associated private key). Wraps the public key into an X.509 v1 self-signed certificate, which is stored as a single-element certificate chain. This certificate chain and the private key are stored in a new keystore entry identified by alias.

keyalg specifies the algorithm to be used to generate the key pair, and keysize specifies the size of each key to be generated. sigalg specifies the algorithm that should be used to sign the self-signed certificate; this algorithm must be compatible with keyalg. See Supported Algorithms and Key Sizes.

dname specifies the X.500 Distinguished Name to be associated with alias, and is used as the issuer and subject fields in the self-signed certificate. If no distinguished name is provided at the command line, the user will be prompted for one.

keypass is a password used to protect the private key of the generated key pair. If no password is provided, the user is prompted for it. If you press RETURN at the prompt, the key password is set to the same password as that used for the keystore. keypass must be at least 6 characters long. Be careful with passwords - see Warning Regarding Passwords.

valDays tells the number of days for which the certificate should be considered valid.

-import {-alias alias} {-file cert_file} [-keypass keypass] {-noprompt} {-trustcacerts} {-storetype storetype} {-keystore keystore} [-storepass storepass] {-v} {-Jjavaoption}

Reads the certificate or certificate chain (where the latter is supplied in a PKCS#7 formatted reply) from the file cert_file, and stores it in the keystore entry identified by alias. If no file is given, the certificate or PKCS#7 reply is read from stdin. keytool can import X.509 v1, v2, and v3 certificates, and PKCS#7 formatted certificate chains consisting of certificates of that type. The data to be imported must be provided either in binary encoding format, or in printable encoding format (also known as Base64 encoding) as defined by the Internet RFC 1421 standard. In the latter case, the encoding must be bounded at the beginning by a string that starts with "-----BEGIN", and bounded at the end by a string that starts with "-----END".

When importing a new trusted certificate, alias must not yet exist in the keystore. Before adding the certificate to the keystore, keytool tries to verify it by attempting to construct a chain of trust from that certificate to a self-signed certificate (belonging to a root CA), using trusted certificates that are already available in the keystore.

If the -trustcacerts option has been specified, additional certificates are considered for the chain of trust, namely the certificates in a file named "cacerts", which resides in the JDK security properties directory, java.home/lib/security, where java.home is the JDK installation directory. The "cacerts" file represents a system-wide keystore with CA certificates. System administrators can configure and manage that file using keytool, specifying "jks" as the keystore type. The "cacerts" keystore file ships with five VeriSign root CA certificates with the following X.500 distinguished names: 

1. OU=Class 1 Public Primary Certification Authority, O="VeriSign, Inc.",
C=US

2. OU=Class 2 Public Primary Certification Authority, O="VeriSign,
Inc.", C=US

3. OU=Class 3 Public Primary Certification Authority,
O="VeriSign, Inc.", C=US

4. OU=Class 4 Public Primary Certification
Authority, O="VeriSign, Inc.", C=US

5. OU=Secure Server Certification
Authority, O="RSA Data Security, Inc.", C=US

The initial password of the "cacerts" keystore file is "changeit". System administrators should change that password and the default access permission of that file upon installing the JDK.

If keytool fails to etablish a trust path from the certificate to be imported up to a self-signed certificate (either from the keystore or the "cacerts" file), the certificate information is printed out, and the user is prompted to verify it, e.g., by comparing the displayed certificate fingerprints with the fingerprints obtained from some other (trusted) source of information, which might be the certificate owner himself/herself. Be very careful to ensure the certificate is valid prior to importing it as a "trusted" certificate! -- see WARNING Re: Importing Trusted Certificates. The user then has the option of aborting the import operation. If the -noprompt option is given, however, there will be no interaction with the user.

When importing a certificate reply, the certificate reply is validated using trusted certificates from the keystore, and optionally using the certificates configured in the "cacerts" keystore file (if the -trustcacerts option was specified).

If the reply is a single X.509 certificate, keytool attempts to establish a trust chain, starting at the certificate reply and ending at a self-signed certificate (belonging to a root CA). The certificate reply and the hierarchy of certificates used to authenticate the certificate reply form the new certificate chain of alias.

If the reply is a PKCS#7 formatted certificate chain, the chain is first ordered (with the user certificate first and the self-signed root CA certificate last), before keytool attempts to match the root CA certificate provided in the reply with any of the trusted certificates in the keystore or the "cacerts" keystore file (if the -trustcacerts option was specified). If no match can be found, the information of the root CA certificate is printed out, and the user is prompted to verify it, e.g., by comparing the displayed certificate fingerprints with the fingerprints obtained from some other (trusted) source of information, which might be the root CA itself. The user then has the option of aborting the import operation. If the -noprompt option is given, however, there will be no interaction with the user.

The new certificate chain of alias replaces the old certificate chain associated with this entry. The old chain can only be replaced if a valid keypass, the password used to protect the private key of the entry, is supplied. If no password is provided, and the private key password is different from the keystore password, the user is prompted for it. Be careful with passwords - see Warning Regarding Passwords.

-selfcert {-alias alias} {-sigalg sigalg} {-dname dname} {-validity valDays} [-keypass keypass] {-storetype storetype} {-keystore keystore} [-storepass storepass] {-v} {-Jjavaoption}

Generates an X.509 v1 self-signed certificate, using keystore information including the private key and public key associated with alias. If dname is supplied at the command line, it is used as the X.500 Distinguished Name for both the issuer and subject of the certificate. Otherwise, the X.500 Distinguished Name associated with alias (at the bottom of its existing certificate chain) is used.

The generated certificate is stored as a single-element certificate chain in the keystore entry identified by alias, where it replaces the existing certificate chain.

sigalg specifies the algorithm that should be used to sign the certificate. See Supported Algorithms and Key Sizes.

In order to access the private key, the appropriate password must be provided, since private keys are protected in the keystore with a password. If keypass is not provided at the command line, and is different from the password used to protect the integrity of the keystore, the user is prompted for it. Be careful with passwords - see Warning Regarding Passwords.

valDays tells the number of days for which the certificate should be considered valid.

-identitydb {-file idb_file} {-storetype storetype} {-keystore keystore} [-storepass storepass] {-v} {-Jjavaoption}

Reads the JDK 1.1.x-style identity database from the file idb_file, and adds its entries to the keystore. If no file is given, the identity database is read from stdin. If a keystore does not exist, it is created.

Only identity database entries ("identities") that were marked as trusted will be imported in the keystore. All other identities will be ignored. For each trusted identity, a keystore entry will be created. The identity's name is used as the "alias" for the keystore entry.

The private keys from trusted identities will all be encrypted under the same password, storepass. This is the same password that is used to protect the keystore's integrity. Users can later assign individual passwords to those private keys by using the "-keypasswd" keytool command option.

An identity in an identity database may hold more than one certificate, each certifying the same public key. But a keystore key entry for a private key has that private key and a single "certificate chain" (initially just a single certificate), where the first certificate in the chain contains the public key corresponding to the private key. When importing the information from an identity, only the first certificate of the identity is stored in the keystore. This is because an identity's name in an identity database is used as the alias for its corresponding keystore entry, and alias names are unique within a keystore,

Exporting Data

-certreq {-alias alias} {-sigalg sigalg} {-file certreq_file} [-keypass keypass] {-storetype storetype} {-keystore keystore} [-storepass storepass] {-v} {-Jjavaoption}

Generates a Certificate Signing Request (CSR), using the PKCS#10 format.

A CSR is intended to be sent to a certificate authority (CA). The CA will authenticate the certificate requestor (usually off-line) and will return a certificate or certificate chain, used to replace the existing certificate chain (which initially consists of a self-signed certificate) in the keystore.

The private key and X.500 Distinguished Name associated with alias are used to create the PKCS#10 certificate request. In order to access the private key, the appropriate password must be provided, since private keys are protected in the keystore with a password. If keypass is not provided at the command line, and is different from the password used to protect the integrity of the keystore, the user is prompted for it.

Be careful with passwords - see Warning Regarding Passwords.

sigalg specifies the algorithm that should be used to sign the CSR. See Supported Algorithms and Key Sizes.

The CSR is stored in the file certreq_file. If no file is given, the CSR is output to stdout.

Use the import command to import the response from the CA.

-export {-alias alias} {-file cert_file} {-storetype storetype} {-keystore keystore} {-storepass storepass} {-rfc} {-v} {-Jjavaoption}

Reads (from the keystore) the certificate associated with alias, and stores it in the file cert_file.

If no file is given, the certificate is output to stdout.

The certificate is by default output in binary encoding, but will instead be output in the printable encoding format, as defined by the Internet RFC 1421 standard, if the -rfc option is specified.

If alias refers to a trusted certificate, that certificate is output. Otherwise, alias refers to a key entry with an associated certificate chain. In that case, the first certificate in the chain is returned. This certificate authenticates the public key of the entity addressed by alias.

Displaying Data

-list {-alias alias} {-storetype storetype} {-keystore keystore} {-storepass storepass} {-v | -rfc} {-Jjavaoption}

Prints (to stdout) the contents of the keystore entry identified by alias. If no alias is specified, the contents of the entire keystore are printed.

This command by default prints the MD5 fingerprint of a certificate. If the -v option is specified, the certificate is printed in human-readable format, while if the -rfc option is specified, certificate contents are printed using the printable encoding format, as defined by the Internet RFC 1421 standard

You cannot specify both -v and -rfc.

-printcert {-file cert_file} {-v} {-Jjavaoption}

Reads the certificate from the file cert_file, and prints its contents in a human-readable format. If no file is given, the certificate is read from stdin.

The certificate may be either binary encoded or in printable encoding format, as defined by the Internet RFC 1421 standard.

Note: This option can be used independently of a keystore.

Managing the Keystore

-keyclone {-alias alias} [-dest dest_alias] [-keypass keypass] [-new new_keypass] {-storetype storetype} {-keystore keystore} [-storepass storepass] {-v} {-Jjavaoption}

Creates a new keystore entry, which has the same private key and certificate chain as the original entry.

The original entry is identified by alias (which defaults to "mykey" if not provided). The new (destination) entry is identified by dest_alias. If no destination alias is supplied at the command line, the user is prompted for it.

If the private key password is different from the keystore password, then the entry will only be cloned if a valid keypass is supplied. This is the password used to protect the private key associated with alias. If no key password is supplied at the command line, and the private key password is different from the keystore password, the user is prompted for it. The private key in the cloned entry may be protected with a different password, if desired. If no -new option is supplied at the command line, the user is prompted for the new entry's password (and may choose to let it be the same as for the cloned entry's private key).

Be careful with passwords - see Warning Regarding Passwords.

This command can be used to establish multiple certificate chains corresponding to a given key pair, or for backup purposes.

-storepasswd {-new new_storepass} {-storetype storetype} {-keystore keystore} [-storepass storepass] {-v} {-Jjavaoption}

Changes the password used to protect the integrity of the keystore contents. The new password is new_storepass, which must be at least 6 characters long.

Be careful with passwords - see Warning Regarding Passwords.

-keypasswd {-alias alias} [-keypass old_keypass] [-new new_keypass] {-storetype storetype} {-keystore keystore} [-storepass storepass] {-v} {-Jjavaoption}

Changes the password under which the private key identified by alias is protected, from old_keypass to new_keypass.

If the -keypass option is not provided at the command line, and the private key password is different from the keystore password, the user is prompted for it.

If the -new option is not provided at the command line, the user is prompted for it.

Be careful with passwords - see Warning Regarding Passwords.

-delete [-alias alias] {-storetype storetype} {-keystore keystore} [-storepass storepass] {-v} {-Jjavaoption}

Deletes from the keystore the entry identified by alias. The user is prompted for the alias, if no alias is provided at the command line.

Getting Help

-help

Lists all the commands and their options.

EXAMPLES

Suppose you want to create a keystore for managing your public/private key pair and certificates from entities you trust.

Generating Your Key Pair

The first thing you need to do is create a keystore and generate the key pair. You could use a command such as the following: 

    keytool -genkey -dname "cn=Mark Jones, ou=JavaSoft, o=Sun, c=US" 
      -alias business -keypass kpi135 -keystore /working/mykeystore 
      -storepass ab987c -validity 180

(Please note: This must be typed as a single line. Multiple lines are used in the examples just for legibility purposes.)

This command creates the keystore named "mykeystore" in the "working" directory (assuming it doesn't already exist), and assigns it the password "ab987c". It generates a public/private key pair for the entity whose "distinguished name" has a common name of "Mark Jones", organizational unit of "JavaSoft", organization of "Sun" and two-letter country code of "US". It uses the default "DSA" key generation algorithm to create the keys, both 1024 bits long.

It creates a self-signed certificate (using the default "SHA1withDSA" signature algorithm) that includes the public key and the distinguished name information. This certificate will be valid for 180 days, and is associated with the private key in a keystore entry referred to by the alias "business". The private key is assigned the password "kpi135".

The command could be significantly shorter if option defaults were accepted. As a matter of fact, no options are required; defaults are used for unspecified options that have default values, and you are prompted for any required values. Thus, you could simply have the following: 

    keytool -genkey
In this case, a keystore entry with alias "mykey" is created, with a newly-generated key pair and a certificate that is valid for 90 days. This entry is placed in the keystore named ".keystore" in your home directory. (The keystore is created if it doesn't already exist.) You will be prompted for the distinguished name information, the keystore password, and the private key password.

The rest of the examples assume you executed the -genkey command without options specified, and that you responded to the prompts with values equal to those given in the first -genkey command, above (a private key password of "kpi135", etc.)

Requesting a Signed Certificate from a Certification Authority

So far all we've got is a self-signed certificate. A certificate is more likely to be trusted by others if it is signed by a Certification Authority (CA). To get such a signature, you first generate a Certificate Signing Request (CSR), via the following: 

    keytool -certreq -file MarkJ.csr
This creates a CSR (for the entity identified by the default alias "mykey") and puts the request in the file named "MarkJ.csr". Submit this file to a CA, such as VeriSign, Inc. The CA will authenticate you, the requestor (usually off-line), and then will return a certificate, signed by them, authenticating your public key. (In some cases, they will actually return a chain of certificates, each one authenticating the public key of the signer of the previous certificate in the chain.)

Importing a Certificate for the CA

You need to replace your self-signed certificate with a certificate chain, where each certificate in the chain authenticates the public key of the signer of the previous certificate in the chain, up to a "root" CA.

But first, you need a "trusted certificate" entry in your keystore (or in the "cacerts" keystore file, as described in importCmd) that authenticates the CA's public key. With such an entry, their signature can be verified. That is, their signature on the certificate, or on the final certificate in the chain they send to you in response to your CSR, can be verified.

The "cacerts" keystore file ships with five VeriSign root CA certificates, so you probably won't need to import a VeriSign certificate as a trusted certificate in your keystore. But if you request a signed certificate from a different CA, and a certificate authenticating that CA's public key hasn't been added to "cacerts", you will need to import a certificate from the CA as a "trusted certificate".

A certificate from a CA is usually either self-signed, or signed by another CA (in which case you also need a certificate authenticating that CA's public key). Suppose company ABC, Inc., is a CA, and you obtain a file named "ABCCA.cer" that is purportedly a self-signed certificate from ABC, authenticating that CA's public key.

Be very careful to ensure the certificate is valid prior to importing it as a "trusted" certificate!

If you trust that this certificate is valid, then you can add it to your keystore via the following: 

    keytool -import -alias abc -file ABCCA.cer
This creates a "trusted certificate" entry in the keystore, with the data from the file "ABCCA.cer", and assigns the alias "abc" to the entry.

Importing the Certificate Reply from the CA

Once you've imported a certificate authenticating the public key of the CA you submitted your certificate signing request to (or there's already such a certificate in the "cacerts" file), you can import the certificate reply and thereby replace your self-signed certificate with a certificate chain. This chain is the one returned by the CA in response to your request (if the CA reply is a chain), or one constructed (if the CA reply is a single certificate) using the certificate reply and trusted certificates that are already available in the keystore where you import the reply or in the "cacerts" keystore file. For example, suppose you sent your certificate signing request to VeriSign. You can then import the reply via the following, which assumes the returned certificate is named "VSMarkJ.cer": 

    keytool -import -trustcacerts -file VSMarkJ.cer

Exporting a Certificate Authenticating Your Public Key

Suppose you have used the jarsigner tool to sign a Java ARchive (JAR) file. Clients that want to use the file will want to authenticate your signature.

In order to do so, they need your public key. You supply this to them by sending them a copy of the certificate authenticating your public key. Copy that certificate to a file named MJ.cer via the following: 

    keytool -export -alias mykey -file MJ.cer
Given that certificate, and the signed JAR file, a client can use the jarsigner tool to authenticate your signature.

Changing Your Distinguished Name but Keeping your Key Pair

Suppose your distinguished name changes, for example because you have changed departments or moved to a different city. If desired, you may still use the public/private key pair you've previously used, and yet update your distinguished name. For example, suppose your name is Susan Miller, and you created your initial key entry with the alias sMiller and the distinguished name 
  "cn=Susan Miller, ou=Finance Department, o=BlueSoft, c=us"
Suppose you change from the Finance Department to the Accounting Department. You can still use the previously-generated public/private key pair and yet update your distinguished name by doing the following. First, copy (clone) your key entry: 
    keytool -keyclone -alias sMiller -dest sMillerNew
(This prompts for the initial and destination private key passwords, since they aren't provided at the command line.) Now you need to change the certificate chain associated with the copy, so that the first certificate in the chain uses your different distinguished name. Start by generating a self-signed certificate with the appropriate name: 
    keytool -selfcert -alias sMillerNew
      -dname "cn=Susan Miller, ou=Accounting Department, o=BlueSoft, c=us"

Then generate a Certificate Signing Request based on the information in this new certificate: 

    keytool -certreq -alias sMillerNew
When you get the CA certificate reply, import it: 
    keytool -import -alias sMillerNew -file VSSMillerNew.cer
After importing the certificate reply, you may want to remove the initial key entry that used your old distinguished name: 
    keytool -delete -alias sMiller

SEE ALSO