1/*
2chacha-merged.c version 20080118
3D. J. Bernstein
4Public domain.
5*/
6
7/* $OpenBSD: chacha_private.h,v 1.2 2013/10/04 07:02:27 djm Exp $ */
8
9typedef unsigned char u8;
10typedef unsigned int u32;
11
12typedef struct
13{
14  u32 input[16]; /* could be compressed */
15} chacha_ctx;
16
17#define U8C(v) (v##U)
18#define U32C(v) (v##U)
19
20#define U8V(v) ((u8)(v) & U8C(0xFF))
21#define U32V(v) ((u32)(v) & U32C(0xFFFFFFFF))
22
23#define ROTL32(v, n) \
24  (U32V((v) << (n)) | ((v) >> (32 - (n))))
25
26#define U8TO32_LITTLE(p) \
27  (((u32)((p)[0])      ) | \
28   ((u32)((p)[1]) <<  8) | \
29   ((u32)((p)[2]) << 16) | \
30   ((u32)((p)[3]) << 24))
31
32#define U32TO8_LITTLE(p, v) \
33  do { \
34    (p)[0] = U8V((v)      ); \
35    (p)[1] = U8V((v) >>  8); \
36    (p)[2] = U8V((v) >> 16); \
37    (p)[3] = U8V((v) >> 24); \
38  } while (0)
39
40#define ROTATE(v,c) (ROTL32(v,c))
41#define XOR(v,w) ((v) ^ (w))
42#define PLUS(v,w) (U32V((v) + (w)))
43#define PLUSONE(v) (PLUS((v),1))
44
45#define QUARTERROUND(a,b,c,d) \
46  a = PLUS(a,b); d = ROTATE(XOR(d,a),16); \
47  c = PLUS(c,d); b = ROTATE(XOR(b,c),12); \
48  a = PLUS(a,b); d = ROTATE(XOR(d,a), 8); \
49  c = PLUS(c,d); b = ROTATE(XOR(b,c), 7);
50
51static const char sigma[16] = "expand 32-byte k";
52static const char tau[16] = "expand 16-byte k";
53
54static void
55chacha_keysetup(chacha_ctx *x,const u8 *k,u32 kbits,u32 ivbits)
56{
57  const char *constants;
58
59  x->input[4] = U8TO32_LITTLE(k + 0);
60  x->input[5] = U8TO32_LITTLE(k + 4);
61  x->input[6] = U8TO32_LITTLE(k + 8);
62  x->input[7] = U8TO32_LITTLE(k + 12);
63  if (kbits == 256) { /* recommended */
64    k += 16;
65    constants = sigma;
66  } else { /* kbits == 128 */
67    constants = tau;
68  }
69  x->input[8] = U8TO32_LITTLE(k + 0);
70  x->input[9] = U8TO32_LITTLE(k + 4);
71  x->input[10] = U8TO32_LITTLE(k + 8);
72  x->input[11] = U8TO32_LITTLE(k + 12);
73  x->input[0] = U8TO32_LITTLE(constants + 0);
74  x->input[1] = U8TO32_LITTLE(constants + 4);
75  x->input[2] = U8TO32_LITTLE(constants + 8);
76  x->input[3] = U8TO32_LITTLE(constants + 12);
77}
78
79static void
80chacha_ivsetup(chacha_ctx *x,const u8 *iv)
81{
82  x->input[12] = 0;
83  x->input[13] = 0;
84  x->input[14] = U8TO32_LITTLE(iv + 0);
85  x->input[15] = U8TO32_LITTLE(iv + 4);
86}
87
88static void
89chacha_encrypt_bytes(chacha_ctx *x,const u8 *m,u8 *c,u32 bytes)
90{
91  u32 x0, x1, x2, x3, x4, x5, x6, x7, x8, x9, x10, x11, x12, x13, x14, x15;
92  u32 j0, j1, j2, j3, j4, j5, j6, j7, j8, j9, j10, j11, j12, j13, j14, j15;
93  u8 *ctarget = NULL;
94  u8 tmp[64];
95  u_int i;
96
97  if (!bytes) return;
98
99  j0 = x->input[0];
100  j1 = x->input[1];
101  j2 = x->input[2];
102  j3 = x->input[3];
103  j4 = x->input[4];
104  j5 = x->input[5];
105  j6 = x->input[6];
106  j7 = x->input[7];
107  j8 = x->input[8];
108  j9 = x->input[9];
109  j10 = x->input[10];
110  j11 = x->input[11];
111  j12 = x->input[12];
112  j13 = x->input[13];
113  j14 = x->input[14];
114  j15 = x->input[15];
115
116  for (;;) {
117    if (bytes < 64) {
118      for (i = 0;i < bytes;++i) tmp[i] = m[i];
119      m = tmp;
120      ctarget = c;
121      c = tmp;
122    }
123    x0 = j0;
124    x1 = j1;
125    x2 = j2;
126    x3 = j3;
127    x4 = j4;
128    x5 = j5;
129    x6 = j6;
130    x7 = j7;
131    x8 = j8;
132    x9 = j9;
133    x10 = j10;
134    x11 = j11;
135    x12 = j12;
136    x13 = j13;
137    x14 = j14;
138    x15 = j15;
139    for (i = 20;i > 0;i -= 2) {
140      QUARTERROUND( x0, x4, x8,x12)
141      QUARTERROUND( x1, x5, x9,x13)
142      QUARTERROUND( x2, x6,x10,x14)
143      QUARTERROUND( x3, x7,x11,x15)
144      QUARTERROUND( x0, x5,x10,x15)
145      QUARTERROUND( x1, x6,x11,x12)
146      QUARTERROUND( x2, x7, x8,x13)
147      QUARTERROUND( x3, x4, x9,x14)
148    }
149    x0 = PLUS(x0,j0);
150    x1 = PLUS(x1,j1);
151    x2 = PLUS(x2,j2);
152    x3 = PLUS(x3,j3);
153    x4 = PLUS(x4,j4);
154    x5 = PLUS(x5,j5);
155    x6 = PLUS(x6,j6);
156    x7 = PLUS(x7,j7);
157    x8 = PLUS(x8,j8);
158    x9 = PLUS(x9,j9);
159    x10 = PLUS(x10,j10);
160    x11 = PLUS(x11,j11);
161    x12 = PLUS(x12,j12);
162    x13 = PLUS(x13,j13);
163    x14 = PLUS(x14,j14);
164    x15 = PLUS(x15,j15);
165
166#ifndef KEYSTREAM_ONLY
167    x0 = XOR(x0,U8TO32_LITTLE(m + 0));
168    x1 = XOR(x1,U8TO32_LITTLE(m + 4));
169    x2 = XOR(x2,U8TO32_LITTLE(m + 8));
170    x3 = XOR(x3,U8TO32_LITTLE(m + 12));
171    x4 = XOR(x4,U8TO32_LITTLE(m + 16));
172    x5 = XOR(x5,U8TO32_LITTLE(m + 20));
173    x6 = XOR(x6,U8TO32_LITTLE(m + 24));
174    x7 = XOR(x7,U8TO32_LITTLE(m + 28));
175    x8 = XOR(x8,U8TO32_LITTLE(m + 32));
176    x9 = XOR(x9,U8TO32_LITTLE(m + 36));
177    x10 = XOR(x10,U8TO32_LITTLE(m + 40));
178    x11 = XOR(x11,U8TO32_LITTLE(m + 44));
179    x12 = XOR(x12,U8TO32_LITTLE(m + 48));
180    x13 = XOR(x13,U8TO32_LITTLE(m + 52));
181    x14 = XOR(x14,U8TO32_LITTLE(m + 56));
182    x15 = XOR(x15,U8TO32_LITTLE(m + 60));
183#endif
184
185    j12 = PLUSONE(j12);
186    if (!j12) {
187      j13 = PLUSONE(j13);
188      /* stopping at 2^70 bytes per nonce is user's responsibility */
189    }
190
191    U32TO8_LITTLE(c + 0,x0);
192    U32TO8_LITTLE(c + 4,x1);
193    U32TO8_LITTLE(c + 8,x2);
194    U32TO8_LITTLE(c + 12,x3);
195    U32TO8_LITTLE(c + 16,x4);
196    U32TO8_LITTLE(c + 20,x5);
197    U32TO8_LITTLE(c + 24,x6);
198    U32TO8_LITTLE(c + 28,x7);
199    U32TO8_LITTLE(c + 32,x8);
200    U32TO8_LITTLE(c + 36,x9);
201    U32TO8_LITTLE(c + 40,x10);
202    U32TO8_LITTLE(c + 44,x11);
203    U32TO8_LITTLE(c + 48,x12);
204    U32TO8_LITTLE(c + 52,x13);
205    U32TO8_LITTLE(c + 56,x14);
206    U32TO8_LITTLE(c + 60,x15);
207
208    if (bytes <= 64) {
209      if (bytes < 64) {
210        for (i = 0;i < bytes;++i) ctarget[i] = c[i];
211      }
212      x->input[12] = j12;
213      x->input[13] = j13;
214      return;
215    }
216    bytes -= 64;
217    c += 64;
218#ifndef KEYSTREAM_ONLY
219    m += 64;
220#endif
221  }
222}
223