50 lines
1.4 KiB
C
50 lines
1.4 KiB
C
#include "chacha.h"
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#define ROTL32(v, n) (((v) << (n)) | ((v) >> (32 - (n))))
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#define ROTATE(v, c) ROTL32((v), (c))
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#define XOR(v, w) ((v) ^ (w))
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#define PLUS(x, y) ((x) + (y))
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#define U32TO8_LITTLE(p, v) \
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{ (p)[0] = ((v) ) & 0xff; (p)[1] = ((v) >> 8) & 0xff; \
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(p)[2] = ((v) >> 16) & 0xff; (p)[3] = ((v) >> 24) & 0xff; }
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#define U8TO32_LITTLE(p) \
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(((u32)((p)[0]) ) | ((u32)((p)[1]) << 8) | \
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((u32)((p)[2]) << 16) | ((u32)((p)[3]) << 24) )
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#define QUARTERROUND(a,b,c,d) \
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x[a] = PLUS(x[a],x[b]); x[d] = ROTATE(XOR(x[d],x[a]),16); \
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x[c] = PLUS(x[c],x[d]); x[b] = ROTATE(XOR(x[b],x[c]),12); \
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x[a] = PLUS(x[a],x[b]); x[d] = ROTATE(XOR(x[d],x[a]), 8); \
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x[c] = PLUS(x[c],x[d]); x[b] = ROTATE(XOR(x[b],x[c]), 7);
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void chacha20_encrypt(const u32 input[16],
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unsigned char output[64],
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int num_rounds)
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{
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u32 x[16];
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int i;
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memcpy(x, input, sizeof(u32) * 16);
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for (i = num_rounds; i > 0; i -= 2) {
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QUARTERROUND( 0, 4, 8,12)
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QUARTERROUND( 1, 5, 9,13)
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QUARTERROUND( 2, 6,10,14)
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QUARTERROUND( 3, 7,11,15)
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QUARTERROUND( 0, 5,10,15)
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QUARTERROUND( 1, 6,11,12)
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QUARTERROUND( 2, 7, 8,13)
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QUARTERROUND( 3, 4, 9,14)
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}
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for (i = 0; i < 16; ++i) {
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x[i] = PLUS(x[i], input[i]);
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}
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for (i = 0; i < 16; ++i) {
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U32TO8_LITTLE(output + 4 * i, x[i]);
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}
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}
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