/*

* Ed25519

* (C) 2017 Ribose Inc

*

* Based on the public domain code from SUPERCOP ref10 by

* Peter Schwabe, Daniel J. Bernstein, Niels Duif, Tanja Lange, Bo-Yin Yang

*

* Botan is released under the Simplified BSD License (see license.txt)

*/

#include <botan/ed25519.h>

#include <botan/internal/ed25519_internal.h>

#include <botan/sha2_64.h>

#include <botan/rng.h>

namespace Botan {

void ed25519_gen_keypair(uint8_t* pk, uint8_t* sk, const uint8_t seed[32])

   {

   uint8_t az[64];

   SHA_512 sha;

   sha.update(seed, 32);

   sha.final(az);

   az[0] &= 248;

   az[31] &= 63;

   az[31] |= 64;

   ge_scalarmult_base(pk, az);

   // todo copy_mem

   copy_mem(sk, seed, 32);

   copy_mem(sk + 32, pk, 32);

   }

void ed25519_sign(uint8_t sig[64],

                  const uint8_t m[], size_t mlen,

                  const uint8_t sk[64],

                  const uint8_t domain_sep[], size_t domain_sep_len)

   {

   uint8_t az[64];

   uint8_t nonce[64];

   uint8_t hram[64];

   SHA_512 sha;

   sha.update(sk, 32);

   sha.final(az);

   az[0] &= 248;

   az[31] &= 63;

   az[31] |= 64;

   sha.update(domain_sep, domain_sep_len);

   sha.update(az + 32, 32);

   sha.update(m, mlen);

   sha.final(nonce);

   sc_reduce(nonce);

   ge_scalarmult_base(sig, nonce);

   sha.update(domain_sep, domain_sep_len);

   sha.update(sig, 32);

   sha.update(sk + 32, 32);

   sha.update(m, mlen);

   sha.final(hram);

   sc_reduce(hram);

   sc_muladd(sig + 32, hram, az, nonce);

   }

bool ed25519_verify(const uint8_t* m, size_t mlen,

                    const uint8_t sig[64],

                    const uint8_t* pk,

                    const uint8_t domain_sep[], size_t domain_sep_len)

   {

   uint8_t h[64];

   uint8_t rcheck[32];

   ge_p3 A;

   SHA_512 sha;

   if(sig[63] & 224)

      {

      return false;

      }

   if(ge_frombytes_negate_vartime(&A, pk) != 0)

      {

      return false;

      }

   sha.update(domain_sep, domain_sep_len);

   sha.update(sig, 32);

   sha.update(pk, 32);

   sha.update(m, mlen);

   sha.final(h);

   sc_reduce(h);

   ge_double_scalarmult_vartime(rcheck, h, &A, sig + 32);

   return constant_time_compare(rcheck, sig, 32);

   }

}