At 4:35 PM -0600 12/20/97, Anonymous wrote:
Can somebody more experienced than I am explain the strengths and weaknesses of these encryption modes as applied to CAST, IDEA, DES, and Blowfish?
-m mode Set the transfer mode.
Valid ENCRYPTION modes are:
ecb Electronic codebook mode c[i] = f1(K, p[i]) p[i] = f2(K, c[i])
cbc Ciphertext block chaining mode c[i] = f1(K, p[i] ^ c[i-1]) p[i] = f2(K, c[i]) ^ c[i-1]
cfb Ciphertext feeback mode c[i] = f1(K, c[i-1]) ^ p[i] p[i] = f2(K, c[i-1]) ^ c[i]
ofb Output feeback mode h[i] = f1(K, h[i-1]) c[i] = p[i] ^ h[i] p[i] = c[i] ^ h[i]
There is a pretty good explanation of the various block cipher modes in Applied Cryptography. Bruce ********************************************************************** Bruce Schneier, President, Counterpane Systems Phone: 612-823-1098 101 E Minnehaha Parkway, Minneapolis,MN 55419 Fax: 612-823-1590 http://www.counterpane.com