January 8, 2002
Practical Aspects of Modern
Cryptography
Karatsuba Multiplication
(Ax+B)(Cx+D) = ACx2 + (AD+BC)x + 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