MMB_Cryptanalysis

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A Boomerang Attack implementation on MMB block cipher

Generate required data

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To generate required plaintexts, we do as follow. First, we generate 2^17 random plaintexts P[0][i] i < 2^17. ‍P[0][i][0] (i.e., first 32-bits word) is a random value for all i and P[0][i][j] j = 1, 2, 3 is a fixed value.

P[1][i] = P[0][i] ^ (0, ~0, 0, ~0.

Then we encrypt P[0] using k[0] and P[1] using k[1]. The result is stored in C[0] and C[1] respectively. We define
C[2] = C[0] ^ (0, 0, ~0, ~0)
C[3] = C[1] ^ (0, 0, ~0, ~0)
P[2] is defined as decryption of C[2] using k[2] as the key. P[3] Defined in the same way.

The code works as follow.

for(uint32_t j = 0; j < bmm.BLOCK_SIZE; j++) {
        P[0][0][j] = rand();
    }
    for(uint32_t i = 0; i < (1<<17); i++){
        // Generate randome plaintexts
        if(i > 0) {
            P[0][i][0] = rand();
            for (int j = 1; j < bmm.BLOCK_SIZE; j++)
                P[0][i][j] = P[0][0][j];
        }
        // P[1] = P[0] ^ (0, ~0, 0, ~0)
        P[1][i][0] = P[0][i][0];
        P[1][i][1] = 0xFFFFFFFF ^ P[0][i][1];
        P[1][i][2] = P[0][i][2];
        P[1][i][3] = 0xFFFFFFFF ^ P[0][i][3];


        // Generate encryption
        bmm.Enc(P[0][i], k[0], C[0][i]);
        bmm.Enc(P[1][i], k[1], C[1][i]);
        // C[2] = C[0] ^ (0, 0, ~0, ~0)
        C[2][i][0] = C[0][i][0];
        C[2][i][1] = C[0][i][1];
        C[2][i][2] = C[0][i][2] ^ 0xFFFFFFFF;
        C[2][i][3] = C[0][i][3] ^ 0xFFFFFFFF;

        // C[3] = C[1] ^ (0, 0, ~0, ~0)
        C[3][i][0] = C[1][i][0];
        C[3][i][1] = C[1][i][1];
        C[3][i][2] = C[1][i][2] ^ 0xFFFFFFFF;
        C[3][i][3] = C[1][i][3] ^ 0xFFFFFFFF;
    }
    for(uint32_t i = 0; i < (1<<17); i++){
        bmm.Dec(C[2][i], k[2], P[2][i]);
        bmm.Dec(C[3][i], k[3], P[3][i]);
    }
}