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/* $OpenBSD: ed25519.c,v 1.2 2013/12/07 00:26:37 djm Exp $ */
/* Public Domain, from supercop-20130419/crypto_sign/ed25519/ref/ed25519.c */
#include "includes.h"
#include "crypto_api.h"
#include "ge25519.h"
static void get_hram(unsigned char *hram, const unsigned char *sm, const unsigned char *pk, unsigned char *playground, unsigned long long smlen)
{
unsigned long long i;
for (i = 0;i < 32;++i) playground[i] = sm[i];
for (i = 32;i < 64;++i) playground[i] = pk[i-32];
for (i = 64;i < smlen;++i) playground[i] = sm[i];
crypto_hash_sha512(hram,playground,smlen);
}
int crypto_sign_ed25519_keypair(
unsigned char *pk,
unsigned char *sk
)
{
sc25519 scsk;
ge25519 gepk;
unsigned char extsk[64];
int i;
randombytes(sk, 32);
crypto_hash_sha512(extsk, sk, 32);
extsk[0] &= 248;
extsk[31] &= 127;
extsk[31] |= 64;
sc25519_from32bytes(&scsk,extsk);
ge25519_scalarmult_base(&gepk, &scsk);
ge25519_pack(pk, &gepk);
for(i=0;i<32;i++)
sk[32 + i] = pk[i];
return 0;
}
int crypto_sign_ed25519(
unsigned char *sm,unsigned long long *smlen,
const unsigned char *m,unsigned long long mlen,
const unsigned char *sk
)
{
sc25519 sck, scs, scsk;
ge25519 ger;
unsigned char r[32];
unsigned char s[32];
unsigned char extsk[64];
unsigned long long i;
unsigned char hmg[crypto_hash_sha512_BYTES];
unsigned char hram[crypto_hash_sha512_BYTES];
crypto_hash_sha512(extsk, sk, 32);
extsk[0] &= 248;
extsk[31] &= 127;
extsk[31] |= 64;
*smlen = mlen+64;
for(i=0;i<mlen;i++)
sm[64 + i] = m[i];
for(i=0;i<32;i++)
sm[32 + i] = extsk[32+i];
crypto_hash_sha512(hmg, sm+32, mlen+32); /* Generate k as h(extsk[32],...,extsk[63],m) */
/* Computation of R */
sc25519_from64bytes(&sck, hmg);
ge25519_scalarmult_base(&ger, &sck);
ge25519_pack(r, &ger);
/* Computation of s */
for(i=0;i<32;i++)
sm[i] = r[i];
get_hram(hram, sm, sk+32, sm, mlen+64);
sc25519_from64bytes(&scs, hram);
sc25519_from32bytes(&scsk, extsk);
sc25519_mul(&scs, &scs, &scsk);
sc25519_add(&scs, &scs, &sck);
sc25519_to32bytes(s,&scs); /* cat s */
for(i=0;i<32;i++)
sm[32 + i] = s[i];
return 0;
}
int crypto_sign_ed25519_open(
unsigned char *m,unsigned long long *mlen,
const unsigned char *sm,unsigned long long smlen,
const unsigned char *pk
)
{
unsigned int i;
int ret;
unsigned char t2[32];
ge25519 get1, get2;
sc25519 schram, scs;
unsigned char hram[crypto_hash_sha512_BYTES];
*mlen = (unsigned long long) -1;
if (smlen < 64) return -1;
if (ge25519_unpackneg_vartime(&get1, pk)) return -1;
get_hram(hram,sm,pk,m,smlen);
sc25519_from64bytes(&schram, hram);
sc25519_from32bytes(&scs, sm+32);
ge25519_double_scalarmult_vartime(&get2, &get1, &schram, &ge25519_base, &scs);
ge25519_pack(t2, &get2);
ret = crypto_verify_32(sm, t2);
if (!ret)
{
for(i=0;i<smlen-64;i++)
m[i] = sm[i + 64];
*mlen = smlen-64;
}
else
{
for(i=0;i<smlen-64;i++)
m[i] = 0;
}
return ret;
}
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