This takes an arbitrary length string and produces a 160-bit [20 byte] value. It takes no command line arguments, reads the string from standard input, computes the hash, and prints the result to standard output.

RIPEMD first extends the string by adding enough padding to get to 8 bytes less than an exact multiple of 64 bytes. The padding consists of a byte of 0x80 followed by as many bytes of 0x00 as are needed. It then appends the 64-bit length of the string in BITS (bits = 8 times number of bytes) in little-endian form. It initialized the array CV [0] through CV [4] to initial values (and I have put these into a file ripemd-consts.c for your use). Then it processes a block of 64 bytes [16 32-bit words] at a time. It calls these 16 words X0 through X15. It copies CV [0] into Al and Ar, CV [1] into Bl and Br, CV [2] into Cl and Cr, CV [3] into Dl and Dr, and CV [4] into El and Er. It does 2 independent 5-round transformations on the X’s: a ”left” set, which works with Al through El, and a ”right” set, which works with Ar through Er. Each round consists of 16 steps. The steps look very similar. Each step consits of the (simutaneous) actions A E, B rollsh amt(ind, j)(A + fj(B,C,D) + Xind + Kj) + E, C B, D rol10(C), and E D. In this Fj(B,C,D) is a function that depends on the round number; on the left side, j is the round number; on the right side, j is 4-the round number. [I.e., in all the steps in round 0 on the left side, use F0; in all the steps in round 0 on the right side, use f4; for round 1, the left side uses f1 and the right side uses f3; etc.] Kj is a constant that depends on the round number and which side (and not the step number). The quantity ind is a permutation of the step number; on the left side, in round 0 it is i, in round 1 it is �(i), in round 2 it is �(�(i)), in round 3 it is �(�(�(i))), and in round 4 it is �(�(�(�(i)))); on the right side, in round 0 it is �(i), in round 1 it is �(�(i)), in round 2 it is �(�(�(i))), in round 3 it is �(�(�(�(i)))), and in round 4 it is �(�(�(�(�(i))))). (In the file ripemd-consts.c I have put arrays K l and K r for the constants K, arrays rho and pi for the permutations � and �, an array lsh amt indexed by the round number and the index of X, an array CV with their initial value, and a (real) function f (round number, B, C, D).) At the end of each block [2 sides of 5 rounds of 16 steps] update the CV array by (simultaneously) doing CV[0] = CV[1] + Cl + Dr, CV[1] = CV[2] + Dl + Er, CV[2] = CV[3] + El + Ar, CV[3] = CV[4] + Al + Br, and CV[4] = CV[0] + Bl + Cr.

==> ripemd

Message: abcdefghijklmnopqrstuvwxyz1234567890ABCDEFGHIJKLMNOPQRSTUVWXYZ

hashcode: 92d8834b48caa12fd79fb995053ef51037d4eadc