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Embedded chacha: Add 0-bit iv + 128-bit counter mode

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This mode might be suitable for a Fortuna keystream primitive.

Reviewed by:	markm
Sponsored by:	Dell EMC Isilon
Differential Revision:	https://reviews.freebsd.org/D19410
This commit is contained in:
cem 2019-03-01 23:30:23 +00:00
parent 99a2719e19
commit e2aca1189b
2 changed files with 43 additions and 1 deletions
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33
sys/crypto/chacha20/chacha.c
View File

@ -84,12 +84,32 @@ chacha_keysetup(chacha_ctx *x,const u8 *k,u32 kbits)
LOCAL void
chacha_ivsetup(chacha_ctx *x, const u8 *iv, const u8 *counter)
{
#ifndef CHACHA_NONCE0_CTR128
x->input[12] = counter == NULL ? 0 : U8TO32_LITTLE(counter + 0);
x->input[13] = counter == NULL ? 0 : U8TO32_LITTLE(counter + 4);
x->input[14] = U8TO32_LITTLE(iv + 0);
x->input[15] = U8TO32_LITTLE(iv + 4);
#else
// CHACHA_STATELEN
(void)iv;
x->input[12] = U8TO32_LITTLE(counter + 0);
x->input[13] = U8TO32_LITTLE(counter + 4);
x->input[14] = U8TO32_LITTLE(counter + 8);
x->input[15] = U8TO32_LITTLE(counter + 12);
#endif
}
#ifdef CHACHA_NONCE0_CTR128
LOCAL void
chacha_ctrsave(const chacha_ctx *x, u8 *counter)
{
U32TO8_LITTLE(counter + 0, x->input[12]);
U32TO8_LITTLE(counter + 4, x->input[13]);
U32TO8_LITTLE(counter + 8, x->input[14]);
U32TO8_LITTLE(counter + 12, x->input[15]);
}
#endif
LOCAL void
chacha_encrypt_bytes(chacha_ctx *x,const u8 *m,u8 *c,u32 bytes)
{
@ -192,7 +212,16 @@ chacha_encrypt_bytes(chacha_ctx *x,const u8 *m,u8 *c,u32 bytes)
j12 = PLUSONE(j12);
if (!j12) {
j13 = PLUSONE(j13);
#ifndef CHACHA_NONCE0_CTR128
/* stopping at 2^70 bytes per nonce is user's responsibility */
#else
if (!j13) {
j14 = PLUSONE(j14);
if (!j14) {
j15 = PLUSONE(j15);
}
}
#endif
}
U32TO8_LITTLE(c + 0,x0);
@ -218,6 +247,10 @@ chacha_encrypt_bytes(chacha_ctx *x,const u8 *m,u8 *c,u32 bytes)
}
x->input[12] = j12;
x->input[13] = j13;
#ifdef CHACHA_NONCE0_CTR128
x->input[14] = j14;
x->input[15] = j15;
#endif
return;
}
bytes -= 64;

11
sys/crypto/chacha20/chacha.h
View File

@ -26,10 +26,19 @@ Public domain.
#define LOCAL
#endif
#ifdef CHACHA_NONCE0_CTR128
#define CHACHA_UNUSED __unused
#else
#define CHACHA_UNUSED
#endif
LOCAL void chacha_keysetup(struct chacha_ctx *x, const u_char *k, u_int kbits);
LOCAL void chacha_ivsetup(struct chacha_ctx *x, const u_char *iv, const u_char *ctr);
LOCAL void chacha_ivsetup(struct chacha_ctx *x, const u_char *iv CHACHA_UNUSED,
const u_char *ctr);
LOCAL void chacha_encrypt_bytes(struct chacha_ctx *x, const u_char *m,
u_char *c, u_int bytes);
#undef CHACHA_UNUSED
#endif /* CHACHA_H */