March 12, 2002
Practical Aspects of Modern Cryptography
62
How Clipper Worked
nClipper was implemented in a tamper-resistant hardware device (a single chip)
nEach chip was numbered and had a separate per-chip secret that was also held by a “trusted agency” (read: US Gov’t)
nPer-session keys were encrypted with a Clipper family key and the per-chip key, and sent along as part of the data stream
nSomeone listening in on the conversation would see enough information to identify the chip used to encrypt, find the per-chip key, and recover the session key