ABC (block cipher)

In cryptography, ABC is a block cipher designed in 2002 by Dieter Schmidt.

ABC is a substitution-permutation network comprising 17 rounds with 3 different kinds of round functions. The first 8 rounds use XORs, modular multiplications as in MMB, and an expanded version of the pseudo-Hadamard transform (PHT) from SAFER. The middle round uses just XORs and multiplications. The final 8 rounds are similar to the first 8, but using the inverse PHT. ABC's block size of 256 bits and key size of 512 bits are both larger than in typical block cipher algorithms. The key schedule is very simple: 256-bit round keys are taken from the key, which is rotated by a fixed amount in each round.

Sample implementation

This Python implementation is used in the Encryption Module Pycrypto:<source lang="python">

1. implementation by douglas funnie used in pycrypto

def MAKEITABC(string,key):

   key         = key+(key*17)
   string      = string+("x00"*(len(string)-len(key)))
   output      = ''
   #SPLIT INTO EVEN LENGTH STRINGS USING Pseudo-Hadamard transform
   dfhusion    = key,key
   salt        = dfhusion+dfhusion+dfhusion+(2*dfhusion)#y
   location    = 0
   for x in range(1,17):
       #COMPARE
       if location >= x:
           location -= 17
       #GET LETTAR
       startKey = string
       #XOR BY KEY
       startKey = chr(ord(startKey)^ord(salt))
       #OG-MMB BY LOC
       startKey = chr(ord(startKey)%(location+1))
       if x == 8:
           salt    =......

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