crypto/openssh/ed25519.c

   1 /* $OpenBSD: ed25519.c,v 1.3 2013/12/09 11:03:45 markus Exp $ */
   2
   3 /*
   4  * Public Domain, Authors: Daniel J. Bernstein, Niels Duif, Tanja Lange,
   5  * Peter Schwabe, Bo-Yin Yang.
   6  * Copied from supercop-20130419/crypto_sign/ed25519/ref/ed25519.c
   7  */
   8
   9 #include "includes.h"
  10 #include "crypto_api.h"
  11
  12 #include "ge25519.h"
  13
  14 static void get_hram(unsigned char *hram, const unsigned char *sm, const unsigned char *pk, unsigned char *playground, unsigned long long smlen)
  15 {
  16   unsigned long long i;
  17
  18   for (i =  0;i < 32;++i)    playground[i] = sm[i];
  19   for (i = 32;i < 64;++i)    playground[i] = pk[i-32];
  20   for (i = 64;i < smlen;++i) playground[i] = sm[i];
  21
  22   crypto_hash_sha512(hram,playground,smlen);
  23 }
  24
  25
  26 int crypto_sign_ed25519_keypair(
  27     unsigned char *pk,
  28     unsigned char *sk
  29     )
  30 {
  31   sc25519 scsk;
  32   ge25519 gepk;
  33   unsigned char extsk[64];
  34   int i;
  35
  36   randombytes(sk, 32);
  37   crypto_hash_sha512(extsk, sk, 32);
  38   extsk[0] &= 248;
  39   extsk[31] &= 127;
  40   extsk[31] |= 64;
  41
  42   sc25519_from32bytes(&scsk,extsk);
  43
  44   ge25519_scalarmult_base(&gepk, &scsk);
  45   ge25519_pack(pk, &gepk);
  46   for(i=0;i<32;i++)
  47     sk[32 + i] = pk[i];
  48   return 0;
  49 }
  50
  51 int crypto_sign_ed25519(
  52     unsigned char *sm,unsigned long long *smlen,
  53     const unsigned char *m,unsigned long long mlen,
  54     const unsigned char *sk
  55     )
  56 {
  57   sc25519 sck, scs, scsk;
  58   ge25519 ger;
  59   unsigned char r[32];
  60   unsigned char s[32];
  61   unsigned char extsk[64];
  62   unsigned long long i;
  63   unsigned char hmg[crypto_hash_sha512_BYTES];
  64   unsigned char hram[crypto_hash_sha512_BYTES];
  65
  66   crypto_hash_sha512(extsk, sk, 32);
  67   extsk[0] &= 248;
  68   extsk[31] &= 127;
  69   extsk[31] |= 64;
  70
  71   *smlen = mlen+64;
  72   for(i=0;i<mlen;i++)
  73     sm[64 + i] = m[i];
  74   for(i=0;i<32;i++)
  75     sm[32 + i] = extsk[32+i];
  76
  77   crypto_hash_sha512(hmg, sm+32, mlen+32); /* Generate k as h(extsk[32],...,extsk[63],m) */
  78
  79   /* Computation of R */
  80   sc25519_from64bytes(&sck, hmg);
  81   ge25519_scalarmult_base(&ger, &sck);
  82   ge25519_pack(r, &ger);
  83
  84   /* Computation of s */
  85   for(i=0;i<32;i++)
  86     sm[i] = r[i];
  87
  88   get_hram(hram, sm, sk+32, sm, mlen+64);
  89
  90   sc25519_from64bytes(&scs, hram);
  91   sc25519_from32bytes(&scsk, extsk);
  92   sc25519_mul(&scs, &scs, &scsk);
  93
  94   sc25519_add(&scs, &scs, &sck);
  95
  96   sc25519_to32bytes(s,&scs); /* cat s */
  97   for(i=0;i<32;i++)
  98     sm[32 + i] = s[i];
  99
 100   return 0;
 101 }
 102
 103 int crypto_sign_ed25519_open(
 104     unsigned char *m,unsigned long long *mlen,
 105     const unsigned char *sm,unsigned long long smlen,
 106     const unsigned char *pk
 107     )
 108 {
 109   unsigned int i;
 110   int ret;
 111   unsigned char t2[32];
 112   ge25519 get1, get2;
 113   sc25519 schram, scs;
 114   unsigned char hram[crypto_hash_sha512_BYTES];
 115
 116   *mlen = (unsigned long long) -1;
 117   if (smlen < 64) return -1;
 118
 119   if (ge25519_unpackneg_vartime(&get1, pk)) return -1;
 120
 121   get_hram(hram,sm,pk,m,smlen);
 122
 123   sc25519_from64bytes(&schram, hram);
 124
 125   sc25519_from32bytes(&scs, sm+32);
 126
 127   ge25519_double_scalarmult_vartime(&get2, &get1, &schram, &ge25519_base, &scs);
 128   ge25519_pack(t2, &get2);
 129
 130   ret = crypto_verify_32(sm, t2);
 131
 132   if (!ret)
 133   {
 134     for(i=0;i<smlen-64;i++)
 135       m[i] = sm[i + 64];
 136     *mlen = smlen-64;
 137   }
 138   else
 139   {
 140     for(i=0;i<smlen-64;i++)
 141       m[i] = 0;
 142   }
 143   return ret;
 144 }