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- /*
- * This code is based on Dan Bernstein's pure C "merged" ChaCha
- * implementation; details below.
- *
- * Note that I've ripped out all of the code that wasn't suitable for doing
- * block-oriented operation, all (residual) support for 128-bit ChaCha keys,
- * all support for counter values over 32 bits, the ability to xor the stream
- * with a plaintext, and so on.
- *
- * Future versions of this might remove bigendian conversions too. DO NOT use
- * this code for your stream cipher: go back to the original source. (I got
- * this copy from SUPERCOP).
- */
-
- /*
- chacha-merged.c version 20080118
- D. J. Bernstein
- Public domain.
- */
- #include <string.h>
- #include "ottery-internal.h"
- #define u8 uint8_t
- #define u32 uint32_t
- #include "chacha_merged_ecrypt.h"
-
- #define ROTATE(v,c) (ROTL32(v,c))
- #define XOR(v,w) ((v) ^ (w))
- #define PLUS(v,w) (U32V((v) + (w)))
- #define PLUSONE(v) (PLUS((v),1))
-
- #define QUARTERROUND(a,b,c,d) \
- a = PLUS(a,b); d = ROTATE(XOR(d,a),16); \
- c = PLUS(c,d); b = ROTATE(XOR(b,c),12); \
- a = PLUS(a,b); d = ROTATE(XOR(d,a), 8); \
- c = PLUS(c,d); b = ROTATE(XOR(b,c), 7);
-
- static const char sigma[16] = "expand 32-byte k";
-
- static void ECRYPT_keysetup(ECRYPT_ctx *x,const u8 *k,u32 ivbits)
- {
- const char *constants;
- (void)ivbits;
-
- x->input[4] = U8TO32_LITTLE(k + 0);
- x->input[5] = U8TO32_LITTLE(k + 4);
- x->input[6] = U8TO32_LITTLE(k + 8);
- x->input[7] = U8TO32_LITTLE(k + 12);
- k += 16;
- constants = sigma;
- x->input[8] = U8TO32_LITTLE(k + 0);
- x->input[9] = U8TO32_LITTLE(k + 4);
- x->input[10] = U8TO32_LITTLE(k + 8);
- x->input[11] = U8TO32_LITTLE(k + 12);
- x->input[0] = U8TO32_LITTLE(constants + 0);
- x->input[1] = U8TO32_LITTLE(constants + 4);
- x->input[2] = U8TO32_LITTLE(constants + 8);
- x->input[3] = U8TO32_LITTLE(constants + 12);
- }
-
- static void ECRYPT_ivsetup(ECRYPT_ctx *x,const u8 *iv)
- {
- x->input[12] = 0;
- x->input[13] = 0;
- x->input[14] = U8TO32_LITTLE(iv + 0);
- x->input[15] = U8TO32_LITTLE(iv + 4);
- }
-
- #define IDX_STEP 16
- #define OUTPUT_LEN (IDX_STEP * 64)
-
- static inline void chacha_merged_getblocks(const int chacha_rounds, ECRYPT_ctx *x,u8 *c) __attribute__((always_inline));
-
- /** Generate OUTPUT_LEN bytes of output using the key, nonce, and counter in x,
- * and store them in c.
- */
- static void chacha_merged_getblocks(const int chacha_rounds, ECRYPT_ctx *x,u8 *c)
- {
- u32 x0, x1, x2, x3, x4, x5, x6, x7, x8, x9, x10, x11, x12, x13, x14, x15;
- u32 j0, j1, j2, j3, j4, j5, j6, j7, j8, j9, j10, j11, j12, j13, j14, j15;
- unsigned i, block;
-
- j0 = x->input[0];
- j1 = x->input[1];
- j2 = x->input[2];
- j3 = x->input[3];
- j4 = x->input[4];
- j5 = x->input[5];
- j6 = x->input[6];
- j7 = x->input[7];
- j8 = x->input[8];
- j9 = x->input[9];
- j10 = x->input[10];
- j11 = x->input[11];
- j12 = x->input[12];
- j13 = x->input[13];
- j14 = x->input[14];
- j15 = x->input[15];
-
- for (block = 0; block < IDX_STEP; ++block) {
- x0 = j0;
- x1 = j1;
- x2 = j2;
- x3 = j3;
- x4 = j4;
- x5 = j5;
- x6 = j6;
- x7 = j7;
- x8 = j8;
- x9 = j9;
- x10 = j10;
- x11 = j11;
- x12 = j12;
- x13 = j13;
- x14 = j14;
- x15 = j15;
- for (i = chacha_rounds;i > 0;i -= 2) {
- QUARTERROUND( x0, x4, x8,x12)
- QUARTERROUND( x1, x5, x9,x13)
- QUARTERROUND( x2, x6,x10,x14)
- QUARTERROUND( x3, x7,x11,x15)
- QUARTERROUND( x0, x5,x10,x15)
- QUARTERROUND( x1, x6,x11,x12)
- QUARTERROUND( x2, x7, x8,x13)
- QUARTERROUND( x3, x4, x9,x14)
- }
- x0 = PLUS(x0,j0);
- x1 = PLUS(x1,j1);
- x2 = PLUS(x2,j2);
- x3 = PLUS(x3,j3);
- x4 = PLUS(x4,j4);
- x5 = PLUS(x5,j5);
- x6 = PLUS(x6,j6);
- x7 = PLUS(x7,j7);
- x8 = PLUS(x8,j8);
- x9 = PLUS(x9,j9);
- x10 = PLUS(x10,j10);
- x11 = PLUS(x11,j11);
- x12 = PLUS(x12,j12);
- x13 = PLUS(x13,j13);
- x14 = PLUS(x14,j14);
- x15 = PLUS(x15,j15);
-
- j12 = PLUSONE(j12);
- /* Ottery: j13 can never need to be incremented. */
-
- U32TO8_LITTLE(c + 0,x0);
- U32TO8_LITTLE(c + 4,x1);
- U32TO8_LITTLE(c + 8,x2);
- U32TO8_LITTLE(c + 12,x3);
- U32TO8_LITTLE(c + 16,x4);
- U32TO8_LITTLE(c + 20,x5);
- U32TO8_LITTLE(c + 24,x6);
-
- U32TO8_LITTLE(c + 28,x7);
- U32TO8_LITTLE(c + 32,x8);
- U32TO8_LITTLE(c + 36,x9);
- U32TO8_LITTLE(c + 40,x10);
- U32TO8_LITTLE(c + 44,x11);
- U32TO8_LITTLE(c + 48,x12);
- U32TO8_LITTLE(c + 52,x13);
- U32TO8_LITTLE(c + 56,x14);
- U32TO8_LITTLE(c + 60,x15);
-
- c += 64;
- }
- }
-
- #define STATE_LEN (sizeof(ECRYPT_ctx))
- #define STATE_BYTES 40
-
- static void
- chacha_merged_state_setup(void *state_, const uint8_t *bytes)
- {
- ECRYPT_ctx *x = state_;
- ECRYPT_keysetup(x, bytes, 0);
- ECRYPT_ivsetup(x, bytes+32);
- }
-
- static void
- chacha8_merged_generate(void *state_, uint8_t *output, uint32_t idx)
- {
- ECRYPT_ctx *x = state_;
- x->input[12] = idx * IDX_STEP;
- chacha_merged_getblocks(8, x, output);
- }
-
- static void
- chacha12_merged_generate(void *state_, uint8_t *output, uint32_t idx)
- {
- ECRYPT_ctx *x = state_;
- x->input[12] = idx * IDX_STEP;
- chacha_merged_getblocks(12, x, output);
- }
-
- static void
- chacha20_merged_generate(void *state_, uint8_t *output, uint32_t idx)
- {
- ECRYPT_ctx *x = state_;
- x->input[12] = idx * IDX_STEP;
- chacha_merged_getblocks(20, x, output);
- }
-
- #define PRF_CHACHA(r) { \
- "CHACHA" #r, \
- "CHACHA" #r "-NOSIMD", \
- "CHACHA" #r "-NOSIMD-DEFAULT", \
- STATE_LEN, \
- STATE_BYTES, \
- OUTPUT_LEN, \
- 0, \
- chacha_merged_state_setup, \
- chacha ## r ## _merged_generate \
- }
-
- const struct ottery_prf ottery_prf_chacha8_merged_ = PRF_CHACHA(8);
- const struct ottery_prf ottery_prf_chacha12_merged_ = PRF_CHACHA(12);
- const struct ottery_prf ottery_prf_chacha20_merged_ = PRF_CHACHA(20);
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