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-rw-r--r--src/crypto/chacha20.cpp180
1 files changed, 180 insertions, 0 deletions
diff --git a/src/crypto/chacha20.cpp b/src/crypto/chacha20.cpp
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+// Copyright (c) 2017 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+// Based on the public domain implementation 'merged' by D. J. Bernstein
+// See https://cr.yp.to/chacha.html.
+
+#include "crypto/common.h"
+#include "crypto/chacha20.h"
+
+#include <string.h>
+
+constexpr static inline uint32_t rotl32(uint32_t v, int c) { return (v << c) | (v >> (32 - c)); }
+
+#define QUARTERROUND(a,b,c,d) \
+ a += b; d = rotl32(d ^ a, 16); \
+ c += d; b = rotl32(b ^ c, 12); \
+ a += b; d = rotl32(d ^ a, 8); \
+ c += d; b = rotl32(b ^ c, 7);
+
+static const unsigned char sigma[] = "expand 32-byte k";
+static const unsigned char tau[] = "expand 16-byte k";
+
+void ChaCha20::SetKey(const unsigned char* k, size_t keylen)
+{
+ const unsigned char *constants;
+
+ input[4] = ReadLE32(k + 0);
+ input[5] = ReadLE32(k + 4);
+ input[6] = ReadLE32(k + 8);
+ input[7] = ReadLE32(k + 12);
+ if (keylen == 32) { /* recommended */
+ k += 16;
+ constants = sigma;
+ } else { /* keylen == 16 */
+ constants = tau;
+ }
+ input[8] = ReadLE32(k + 0);
+ input[9] = ReadLE32(k + 4);
+ input[10] = ReadLE32(k + 8);
+ input[11] = ReadLE32(k + 12);
+ input[0] = ReadLE32(constants + 0);
+ input[1] = ReadLE32(constants + 4);
+ input[2] = ReadLE32(constants + 8);
+ input[3] = ReadLE32(constants + 12);
+ input[12] = 0;
+ input[13] = 0;
+ input[14] = 0;
+ input[15] = 0;
+}
+
+ChaCha20::ChaCha20()
+{
+ memset(input, 0, sizeof(input));
+}
+
+ChaCha20::ChaCha20(const unsigned char* k, size_t keylen)
+{
+ SetKey(k, keylen);
+}
+
+void ChaCha20::SetIV(uint64_t iv)
+{
+ input[14] = iv;
+ input[15] = iv >> 32;
+}
+
+void ChaCha20::Seek(uint64_t pos)
+{
+ input[12] = pos;
+ input[13] = pos >> 32;
+}
+
+void ChaCha20::Output(unsigned char* c, size_t bytes)
+{
+ uint32_t x0, x1, x2, x3, x4, x5, x6, x7, x8, x9, x10, x11, x12, x13, x14, x15;
+ uint32_t j0, j1, j2, j3, j4, j5, j6, j7, j8, j9, j10, j11, j12, j13, j14, j15;
+ unsigned char *ctarget = NULL;
+ unsigned char tmp[64];
+ unsigned int i;
+
+ if (!bytes) return;
+
+ j0 = input[0];
+ j1 = input[1];
+ j2 = input[2];
+ j3 = input[3];
+ j4 = input[4];
+ j5 = input[5];
+ j6 = input[6];
+ j7 = input[7];
+ j8 = input[8];
+ j9 = input[9];
+ j10 = input[10];
+ j11 = input[11];
+ j12 = input[12];
+ j13 = input[13];
+ j14 = input[14];
+ j15 = input[15];
+
+ for (;;) {
+ if (bytes < 64) {
+ ctarget = c;
+ c = tmp;
+ }
+ 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 = 20;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 += 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;
+
+ ++j12;
+ if (!j12) ++j13;
+
+ WriteLE32(c + 0, x0);
+ WriteLE32(c + 4, x1);
+ WriteLE32(c + 8, x2);
+ WriteLE32(c + 12, x3);
+ WriteLE32(c + 16, x4);
+ WriteLE32(c + 20, x5);
+ WriteLE32(c + 24, x6);
+ WriteLE32(c + 28, x7);
+ WriteLE32(c + 32, x8);
+ WriteLE32(c + 36, x9);
+ WriteLE32(c + 40, x10);
+ WriteLE32(c + 44, x11);
+ WriteLE32(c + 48, x12);
+ WriteLE32(c + 52, x13);
+ WriteLE32(c + 56, x14);
+ WriteLE32(c + 60, x15);
+
+ if (bytes <= 64) {
+ if (bytes < 64) {
+ for (i = 0;i < bytes;++i) ctarget[i] = c[i];
+ }
+ input[12] = j12;
+ input[13] = j13;
+ return;
+ }
+ bytes -= 64;
+ c += 64;
+ }
+}