January 8, 2002
Practical Aspects of Modern
Cryptography
Karatsuba Multiplication
(A•2k+B)(C•2k+D) =
• AC•22k +
(AD+BC)•2k + BD
4 multiplications, 1
addition
(A+B)(C+D) = AC + AD + BC + BD
(A+B)(C+D) – AC – BD = AD + BC
3 multiplications, 2
additions, 2 subtractions