bip32.c

/**
 * Copyright (c) 2013-2016 Tomas Dzetkulic
 * Copyright (c) 2013-2016 Pavol Rusnak
 * Copyright (c) 2015-2016 Jochen Hoenicke
 *
 * Permission is hereby granted, free of charge, to any person obtaining
 * a copy of this software and associated documentation files (the "Software"),
 * to deal in the Software without restriction, including without limitation
 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
 * and/or sell copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included
 * in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES
 * OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 */

#include <stdbool.h>
#include <string.h>

#include "address.h"
#include "aes/aes.h"
#include "base58.h"
#include "bignum.h"
#include "bip32.h"
#include "curves.h"
#include "ecdsa.h"
#include "ed25519-donna/ed25519-sha3.h"
#include "ed25519-donna/ed25519.h"
#include "hmac.h"
#include "nist256p1.h"
#include "secp256k1.h"
#include "sha2.h"
#include "sha3.h"
#if USE_KECCAK
#include "ed25519-donna/ed25519-keccak.h"
#endif
#if USE_NEM
#include "nem.h"
#endif
#if USE_CARDANO
#include "pbkdf2.h"
#endif
#include "memzero.h"

#define CARDANO_MAX_NODE_DEPTH 1048576

const curve_info ed25519_info = {
    .bip32_name = "ed25519 seed",
    .params = NULL,
    .hasher_base58 = HASHER_SHA2D,
    .hasher_sign = HASHER_SHA2D,
    .hasher_pubkey = HASHER_SHA2_RIPEMD,
    .hasher_script = HASHER_SHA2,
};

const curve_info ed25519_cardano_info = {
    .bip32_name = "ed25519 cardano seed",
    .params = NULL,
    .hasher_base58 = HASHER_SHA2D,
    .hasher_sign = HASHER_SHA2D,
    .hasher_pubkey = HASHER_SHA2_RIPEMD,
    .hasher_script = HASHER_SHA2,
};

const curve_info ed25519_sha3_info = {
    .bip32_name = "ed25519-sha3 seed",
    .params = NULL,
    .hasher_base58 = HASHER_SHA2D,
    .hasher_sign = HASHER_SHA2D,
    .hasher_pubkey = HASHER_SHA2_RIPEMD,
    .hasher_script = HASHER_SHA2,
};

#if USE_KECCAK
const curve_info ed25519_keccak_info = {
    .bip32_name = "ed25519-keccak seed",
    .params = NULL,
    .hasher_base58 = HASHER_SHA2D,
    .hasher_sign = HASHER_SHA2D,
    .hasher_pubkey = HASHER_SHA2_RIPEMD,
    .hasher_script = HASHER_SHA2,
};
#endif

const curve_info curve25519_info = {
    .bip32_name = "curve25519 seed",
    .params = NULL,
    .hasher_base58 = HASHER_SHA2D,
    .hasher_sign = HASHER_SHA2D,
    .hasher_pubkey = HASHER_SHA2_RIPEMD,
    .hasher_script = HASHER_SHA2,
};

int hdnode_from_xpub(uint32_t depth, uint32_t child_num,
                     const uint8_t *chain_code, const uint8_t *public_key,
                     const char *curve, HDNode *out) {
  const curve_info *info = get_curve_by_name(curve);
  if (info == 0) {
    return 0;
  }
  if (public_key[0] != 0x02 && public_key[0] != 0x03) {  // invalid pubkey
    return 0;
  }
  out->curve = info;
  out->depth = depth;
  out->child_num = child_num;
  memcpy(out->chain_code, chain_code, 32);
  memzero(out->private_key, 32);
  memzero(out->private_key_extension, 32);
  memcpy(out->public_key, public_key, 33);
  return 1;
}

int hdnode_from_xprv(uint32_t depth, uint32_t child_num,
                     const uint8_t *chain_code, const uint8_t *private_key,
                     const char *curve, HDNode *out) {
  bool failed = false;
  const curve_info *info = get_curve_by_name(curve);
  if (info == 0) {
    failed = true;
  } else if (info->params) {
    bignum256 a;
    bn_read_be(private_key, &a);
    if (bn_is_zero(&a)) {  // == 0
      failed = true;
    } else {
      if (!bn_is_less(&a, &info->params->order)) {  // >= order
        failed = true;
      }
    }
    memzero(&a, sizeof(a));
  }

  if (failed) {
    return 0;
  }

  out->curve = info;
  out->depth = depth;
  out->child_num = child_num;
  memcpy(out->chain_code, chain_code, 32);
  memcpy(out->private_key, private_key, 32);
  memzero(out->public_key, sizeof(out->public_key));
  memzero(out->private_key_extension, sizeof(out->private_key_extension));
  return 1;
}

int hdnode_from_seed(const uint8_t *seed, int seed_len, const char *curve,
                     HDNode *out) {
  static CONFIDENTIAL uint8_t I[32 + 32];
  memzero(out, sizeof(HDNode));
  out->depth = 0;
  out->child_num = 0;
  out->curve = get_curve_by_name(curve);
  if (out->curve == 0) {
    return 0;
  }
  static CONFIDENTIAL HMAC_SHA512_CTX ctx;
  hmac_sha512_Init(&ctx, (const uint8_t *)out->curve->bip32_name,
                   strlen(out->curve->bip32_name));
  hmac_sha512_Update(&ctx, seed, seed_len);
  hmac_sha512_Final(&ctx, I);

  if (out->curve->params) {
    bignum256 a;
    while (true) {
      bn_read_be(I, &a);
      if (!bn_is_zero(&a)                                   // != 0
          && bn_is_less(&a, &out->curve->params->order)) {  // < order
        break;
      }
      hmac_sha512_Init(&ctx, (const uint8_t *)out->curve->bip32_name,
                       strlen(out->curve->bip32_name));
      hmac_sha512_Update(&ctx, I, sizeof(I));
      hmac_sha512_Final(&ctx, I);
    }
    memzero(&a, sizeof(a));
  }
  memcpy(out->private_key, I, 32);
  memcpy(out->chain_code, I + 32, 32);
  memzero(out->public_key, sizeof(out->public_key));
  memzero(I, sizeof(I));
  return 1;
}

uint32_t hdnode_fingerprint(HDNode *node) {
  uint8_t digest[32];
  uint32_t fingerprint;

  hdnode_fill_public_key(node);
  hasher_Raw(node->curve->hasher_pubkey, node->public_key, 33, digest);
  fingerprint = ((uint32_t)digest[0] << 24) + (digest[1] << 16) +
                (digest[2] << 8) + digest[3];
  memzero(digest, sizeof(digest));
  return fingerprint;
}

int hdnode_private_ckd(HDNode *inout, uint32_t i) {
  static CONFIDENTIAL uint8_t data[1 + 32 + 4];
  static CONFIDENTIAL uint8_t I[32 + 32];
  static CONFIDENTIAL bignum256 a, b;

  if (i & 0x80000000) {  // private derivation
    data[0] = 0;
    memcpy(data + 1, inout->private_key, 32);
  } else {  // public derivation
    if (!inout->curve->params) {
      return 0;
    }
    hdnode_fill_public_key(inout);
    memcpy(data, inout->public_key, 33);
  }
  write_be(data + 33, i);

  bn_read_be(inout->private_key, &a);

  static CONFIDENTIAL HMAC_SHA512_CTX ctx;
  hmac_sha512_Init(&ctx, inout->chain_code, 32);
  hmac_sha512_Update(&ctx, data, sizeof(data));
  hmac_sha512_Final(&ctx, I);

  if (inout->curve->params) {
    while (true) {
      bool failed = false;
      bn_read_be(I, &b);
      if (!bn_is_less(&b, &inout->curve->params->order)) {  // >= order
        failed = true;
      } else {
        bn_add(&b, &a);
        bn_mod(&b, &inout->curve->params->order);
        if (bn_is_zero(&b)) {
          failed = true;
        }
      }

      if (!failed) {
        bn_write_be(&b, inout->private_key);
        break;
      }

      data[0] = 1;
      memcpy(data + 1, I + 32, 32);
      hmac_sha512_Init(&ctx, inout->chain_code, 32);
      hmac_sha512_Update(&ctx, data, sizeof(data));
      hmac_sha512_Final(&ctx, I);
    }
  } else {
    memcpy(inout->private_key, I, 32);
  }

  memcpy(inout->chain_code, I + 32, 32);
  inout->depth++;
  inout->child_num = i;
  memzero(inout->public_key, sizeof(inout->public_key));

  // making sure to wipe our memory
  memzero(&a, sizeof(a));
  memzero(&b, sizeof(b));
  memzero(I, sizeof(I));
  memzero(data, sizeof(data));
  return 1;
}

#if USE_CARDANO
static void scalar_multiply8(const uint8_t *src, int bytes, uint8_t *dst) {
  uint8_t prev_acc = 0;
  for (int i = 0; i < bytes; i++) {
    dst[i] = (src[i] << 3) + (prev_acc & 0x7);
    prev_acc = src[i] >> 5;
  }
  dst[bytes] = src[bytes - 1] >> 5;
}

static void scalar_add_256bits(const uint8_t *src1, const uint8_t *src2,
                               uint8_t *dst) {
  uint16_t r = 0;
  for (int i = 0; i < 32; i++) {
    r = r + (uint16_t)src1[i] + (uint16_t)src2[i];
    dst[i] = r & 0xff;
    r >>= 8;
  }
}

int hdnode_private_ckd_cardano(HDNode *inout, uint32_t index) {
  if (inout->depth >= CARDANO_MAX_NODE_DEPTH) {
    return 0;
  }

  // checks for hardened/non-hardened derivation, keysize 32 means we are
  // dealing with public key and thus non-h, keysize 64 is for private key
  int keysize = 32;
  if (index & 0x80000000) {
    keysize = 64;
  }

  static CONFIDENTIAL uint8_t data[1 + 64 + 4];
  static CONFIDENTIAL uint8_t z[32 + 32];
  static CONFIDENTIAL uint8_t priv_key[64];
  static CONFIDENTIAL uint8_t res_key[64];

  write_le(data + keysize + 1, index);

  memcpy(priv_key, inout->private_key, 32);
  memcpy(priv_key + 32, inout->private_key_extension, 32);

  if (keysize == 64) {  // private derivation
    data[0] = 0;
    memcpy(data + 1, inout->private_key, 32);
    memcpy(data + 1 + 32, inout->private_key_extension, 32);
  } else {  // public derivation
    hdnode_fill_public_key(inout);
    data[0] = 2;
    memcpy(data + 1, inout->public_key + 1, 32);
  }

  static CONFIDENTIAL HMAC_SHA512_CTX ctx;
  hmac_sha512_Init(&ctx, inout->chain_code, 32);
  hmac_sha512_Update(&ctx, data, 1 + keysize + 4);
  hmac_sha512_Final(&ctx, z);

  static CONFIDENTIAL uint8_t zl8[32];
  memzero(zl8, 32);

  /* get 8 * Zl */
  scalar_multiply8(z, 28, zl8);
  /* Kl = 8*Zl + parent(K)l */
  scalar_add_256bits(zl8, priv_key, res_key);

  /* Kr = Zr + parent(K)r */
  scalar_add_256bits(z + 32, priv_key + 32, res_key + 32);

  memcpy(inout->private_key, res_key, 32);
  memcpy(inout->private_key_extension, res_key + 32, 32);

  if (keysize == 64) {
    data[0] = 1;
  } else {
    data[0] = 3;
  }
  hmac_sha512_Init(&ctx, inout->chain_code, 32);
  hmac_sha512_Update(&ctx, data, 1 + keysize + 4);
  hmac_sha512_Final(&ctx, z);

  memcpy(inout->chain_code, z + 32, 32);
  inout->depth++;
  inout->child_num = index;
  memzero(inout->public_key, sizeof(inout->public_key));

  // making sure to wipe our memory
  memzero(z, sizeof(z));
  memzero(data, sizeof(data));
  memzero(priv_key, sizeof(priv_key));
  memzero(res_key, sizeof(res_key));
  return 1;
}

static int hdnode_from_secret_cardano(const uint8_t *k,
                                      const uint8_t *chain_code, HDNode *out) {
  memzero(out, sizeof(HDNode));
  out->depth = 0;
  out->child_num = 0;
  out->curve = &ed25519_cardano_info;
  memcpy(out->private_key, k, 32);
  memcpy(out->private_key_extension, k + 32, 32);
  memcpy(out->chain_code, chain_code, 32);

  out->private_key[0] &= 0xf8;
  out->private_key[31] &= 0x1f;
  out->private_key[31] |= 0x40;

  out->public_key[0] = 0;
  hdnode_fill_public_key(out);

  return 1;
}

// Derives the root Cardano HDNode from a master secret, aka seed, as defined in
// SLIP-0023.
int hdnode_from_seed_cardano(const uint8_t *seed, int seed_len, HDNode *out) {
  static CONFIDENTIAL uint8_t I[SHA512_DIGEST_LENGTH];
  static CONFIDENTIAL uint8_t k[SHA512_DIGEST_LENGTH];
  static CONFIDENTIAL HMAC_SHA512_CTX ctx;

  hmac_sha512_Init(&ctx, (const uint8_t *)ED25519_CARDANO_NAME,
                   strlen(ED25519_CARDANO_NAME));
  hmac_sha512_Update(&ctx, seed, seed_len);
  hmac_sha512_Final(&ctx, I);

  sha512_Raw(I, 32, k);

  int ret = hdnode_from_secret_cardano(k, I + 32, out);

  memzero(I, sizeof(I));
  memzero(k, sizeof(k));
  memzero(&ctx, sizeof(ctx));
  return ret;
}

// Derives the root Cardano HDNode from a passphrase and the entropy encoded in
// a BIP-0039 mnemonic using the Icarus derivation scheme, aka V2 derivation
// scheme.
int hdnode_from_entropy_cardano_icarus(const uint8_t *pass, int pass_len,
                                       const uint8_t *entropy, int entropy_len,
                                       HDNode *out) {
  static CONFIDENTIAL uint8_t secret[96];
  pbkdf2_hmac_sha512(pass, pass_len, entropy, entropy_len, 4096, secret, 96);

  int ret = hdnode_from_secret_cardano(secret, secret + 64, out);
  memzero(secret, sizeof(secret));
  return ret;
}
#endif

int hdnode_public_ckd_cp(const ecdsa_curve *curve, const curve_point *parent,
                         const uint8_t *parent_chain_code, uint32_t i,
                         curve_point *child, uint8_t *child_chain_code) {
  uint8_t data[1 + 32 + 4];
  uint8_t I[32 + 32];
  bignum256 c;

  if (i & 0x80000000) {  // private derivation
    return 0;
  }

  data[0] = 0x02 | (parent->y.val[0] & 0x01);
  bn_write_be(&parent->x, data + 1);
  write_be(data + 33, i);

  while (true) {
    hmac_sha512(parent_chain_code, 32, data, sizeof(data), I);
    bn_read_be(I, &c);
    if (bn_is_less(&c, &curve->order)) {  // < order
      scalar_multiply(curve, &c, child);  // b = c * G
      point_add(curve, parent, child);    // b = a + b
      if (!point_is_infinity(child)) {
        if (child_chain_code) {
          memcpy(child_chain_code, I + 32, 32);
        }

        // Wipe all stack data.
        memzero(data, sizeof(data));
        memzero(I, sizeof(I));
        memzero(&c, sizeof(c));
        return 1;
      }
    }

    data[0] = 1;
    memcpy(data + 1, I + 32, 32);
  }
}

int hdnode_public_ckd(HDNode *inout, uint32_t i) {
  curve_point parent, child;

  if (!ecdsa_read_pubkey(inout->curve->params, inout->public_key, &parent)) {
    return 0;
  }
  if (!hdnode_public_ckd_cp(inout->curve->params, &parent, inout->chain_code, i,
                            &child, inout->chain_code)) {
    return 0;
  }
  memzero(inout->private_key, 32);
  inout->depth++;
  inout->child_num = i;
  inout->public_key[0] = 0x02 | (child.y.val[0] & 0x01);
  bn_write_be(&child.x, inout->public_key + 1);

  // Wipe all stack data.
  memzero(&parent, sizeof(parent));
  memzero(&child, sizeof(child));

  return 1;
}

void hdnode_public_ckd_address_optimized(const curve_point *pub,
                                         const uint8_t *chain_code, uint32_t i,
                                         uint32_t version,
                                         HasherType hasher_pubkey,
                                         HasherType hasher_base58, char *addr,
                                         int addrsize, int addrformat) {
  uint8_t child_pubkey[33];
  curve_point b;

  hdnode_public_ckd_cp(&secp256k1, pub, chain_code, i, &b, NULL);
  child_pubkey[0] = 0x02 | (b.y.val[0] & 0x01);
  bn_write_be(&b.x, child_pubkey + 1);

  switch (addrformat) {
    case 1:  // Segwit-in-P2SH
      ecdsa_get_address_segwit_p2sh(child_pubkey, version, hasher_pubkey,
                                    hasher_base58, addr, addrsize);
      break;
    default:  // normal address
      ecdsa_get_address(child_pubkey, version, hasher_pubkey, hasher_base58,
                        addr, addrsize);
      break;
  }
}

#if USE_BIP32_CACHE
static bool private_ckd_cache_root_set = false;
static CONFIDENTIAL HDNode private_ckd_cache_root;
static int private_ckd_cache_index = 0;

static CONFIDENTIAL struct {
  bool set;
  size_t depth;
  uint32_t i[BIP32_CACHE_MAXDEPTH];
  HDNode node;
} private_ckd_cache[BIP32_CACHE_SIZE];

int hdnode_private_ckd_cached(HDNode *inout, const uint32_t *i, size_t i_count,
                              uint32_t *fingerprint) {
  if (i_count == 0) {
    // no way how to compute parent fingerprint
    return 1;
  }
  if (i_count == 1) {
    if (fingerprint) {
      *fingerprint = hdnode_fingerprint(inout);
    }
    if (hdnode_private_ckd(inout, i[0]) == 0) return 0;
    return 1;
  }

  bool found = false;
  // if root is not set or not the same
  if (!private_ckd_cache_root_set ||
      memcmp(&private_ckd_cache_root, inout, sizeof(HDNode)) != 0) {
    // clear the cache
    private_ckd_cache_index = 0;
    memzero(private_ckd_cache, sizeof(private_ckd_cache));
    // setup new root
    memcpy(&private_ckd_cache_root, inout, sizeof(HDNode));
    private_ckd_cache_root_set = true;
  } else {
    // try to find parent
    int j;
    for (j = 0; j < BIP32_CACHE_SIZE; j++) {
      if (private_ckd_cache[j].set &&
          private_ckd_cache[j].depth == i_count - 1 &&
          memcmp(private_ckd_cache[j].i, i, (i_count - 1) * sizeof(uint32_t)) ==
              0 &&
          private_ckd_cache[j].node.curve == inout->curve) {
        memcpy(inout, &(private_ckd_cache[j].node), sizeof(HDNode));
        found = true;
        break;
      }
    }
  }

  // else derive parent
  if (!found) {
    size_t k;
    for (k = 0; k < i_count - 1; k++) {
      if (hdnode_private_ckd(inout, i[k]) == 0) return 0;
    }
    // and save it
    memzero(&(private_ckd_cache[private_ckd_cache_index]),
            sizeof(private_ckd_cache[private_ckd_cache_index]));
    private_ckd_cache[private_ckd_cache_index].set = true;
    private_ckd_cache[private_ckd_cache_index].depth = i_count - 1;
    memcpy(private_ckd_cache[private_ckd_cache_index].i, i,
           (i_count - 1) * sizeof(uint32_t));
    memcpy(&(private_ckd_cache[private_ckd_cache_index].node), inout,
           sizeof(HDNode));
    private_ckd_cache_index = (private_ckd_cache_index + 1) % BIP32_CACHE_SIZE;
  }

  if (fingerprint) {
    *fingerprint = hdnode_fingerprint(inout);
  }
  if (hdnode_private_ckd(inout, i[i_count - 1]) == 0) return 0;

  return 1;
}
#endif

void hdnode_get_address_raw(HDNode *node, uint32_t version, uint8_t *addr_raw) {
  hdnode_fill_public_key(node);
  ecdsa_get_address_raw(node->public_key, version, node->curve->hasher_pubkey,
                        addr_raw);
}

void hdnode_get_address(HDNode *node, uint32_t version, char *addr,
                        int addrsize) {
  hdnode_fill_public_key(node);
  ecdsa_get_address(node->public_key, version, node->curve->hasher_pubkey,
                    node->curve->hasher_base58, addr, addrsize);
}

void hdnode_fill_public_key(HDNode *node) {
  if (node->public_key[0] != 0) return;

#if USE_BIP32_25519_CURVES
  if (node->curve->params) {
    ecdsa_get_public_key33(node->curve->params, node->private_key,
                           node->public_key);
  } else {
    node->public_key[0] = 1;
    if (node->curve == &ed25519_info) {
      ed25519_publickey(node->private_key, node->public_key + 1);
    } else if (node->curve == &ed25519_sha3_info) {
      ed25519_publickey_sha3(node->private_key, node->public_key + 1);
#if USE_KECCAK
    } else if (node->curve == &ed25519_keccak_info) {
      ed25519_publickey_keccak(node->private_key, node->public_key + 1);
#endif
    } else if (node->curve == &curve25519_info) {
      curve25519_scalarmult_basepoint(node->public_key + 1, node->private_key);
#if USE_CARDANO
    } else if (node->curve == &ed25519_cardano_info) {
      ed25519_publickey_ext(node->private_key, node->private_key_extension,
                            node->public_key + 1);
#endif
    }
  }
#else

  ecdsa_get_public_key33(node->curve->params, node->private_key,
                         node->public_key);
#endif
}

#if USE_ETHEREUM
int hdnode_get_ethereum_pubkeyhash(const HDNode *node, uint8_t *pubkeyhash) {
  uint8_t buf[65];
  SHA3_CTX ctx;

  /* get uncompressed public key */
  ecdsa_get_public_key65(node->curve->params, node->private_key, buf);

  /* compute sha3 of x and y coordinate without 04 prefix */
  sha3_256_Init(&ctx);
  sha3_Update(&ctx, buf + 1, 64);
  keccak_Final(&ctx, buf);

  /* result are the least significant 160 bits */
  memcpy(pubkeyhash, buf + 12, 20);

  return 1;
}
#endif

#if USE_NEM
int hdnode_get_nem_address(HDNode *node, uint8_t version, char *address) {
  if (node->curve != &ed25519_keccak_info) {
    return 0;
  }

  hdnode_fill_public_key(node);
  return nem_get_address(&node->public_key[1], version, address);
}

int hdnode_get_nem_shared_key(const HDNode *node,
                              const ed25519_public_key peer_public_key,
                              const uint8_t *salt, ed25519_public_key mul,
                              uint8_t *shared_key) {
  if (node->curve != &ed25519_keccak_info) {
    return 0;
  }

  // sizeof(ed25519_public_key) == SHA3_256_DIGEST_LENGTH
  if (mul == NULL) mul = shared_key;

  if (ed25519_scalarmult_keccak(mul, node->private_key, peer_public_key)) {
    return 0;
  }

  for (size_t i = 0; i < 32; i++) {
    shared_key[i] = mul[i] ^ salt[i];
  }

  keccak_256(shared_key, 32, shared_key);
  return 1;
}

int hdnode_nem_encrypt(const HDNode *node, const ed25519_public_key public_key,
                       const uint8_t *iv_immut, const uint8_t *salt,
                       const uint8_t *payload, size_t size, uint8_t *buffer) {
  uint8_t last_block[AES_BLOCK_SIZE];
  uint8_t remainder = size % AES_BLOCK_SIZE;

  // Round down to last whole block
  size -= remainder;
  // Copy old last block
  memcpy(last_block, &payload[size], remainder);
  // Pad new last block with number of missing bytes
  memset(&last_block[remainder], AES_BLOCK_SIZE - remainder,
         AES_BLOCK_SIZE - remainder);

  // the IV gets mutated, so we make a copy not to touch the original
  uint8_t iv[AES_BLOCK_SIZE];
  memcpy(iv, iv_immut, AES_BLOCK_SIZE);

  uint8_t shared_key[SHA3_256_DIGEST_LENGTH];
  if (!hdnode_get_nem_shared_key(node, public_key, salt, NULL, shared_key)) {
    return 0;
  }

  aes_encrypt_ctx ctx;

  int ret = aes_encrypt_key256(shared_key, &ctx);
  memzero(shared_key, sizeof(shared_key));

  if (ret != EXIT_SUCCESS) {
    return 0;
  }

  if (aes_cbc_encrypt(payload, buffer, size, iv, &ctx) != EXIT_SUCCESS) {
    return 0;
  }

  if (aes_cbc_encrypt(last_block, &buffer[size], sizeof(last_block), iv,
                      &ctx) != EXIT_SUCCESS) {
    return 0;
  }

  return 1;
}

int hdnode_nem_decrypt(const HDNode *node, const ed25519_public_key public_key,
                       uint8_t *iv, const uint8_t *salt, const uint8_t *payload,
                       size_t size, uint8_t *buffer) {
  uint8_t shared_key[SHA3_256_DIGEST_LENGTH];

  if (!hdnode_get_nem_shared_key(node, public_key, salt, NULL, shared_key)) {
    return 0;
  }

  aes_decrypt_ctx ctx;

  int ret = aes_decrypt_key256(shared_key, &ctx);
  memzero(shared_key, sizeof(shared_key));

  if (ret != EXIT_SUCCESS) {
    return 0;
  }

  if (aes_cbc_decrypt(payload, buffer, size, iv, &ctx) != EXIT_SUCCESS) {
    return 0;
  }

  return 1;
}
#endif

// msg is a data to be signed
// msg_len is the message length
int hdnode_sign(HDNode *node, const uint8_t *msg, uint32_t msg_len,
                HasherType hasher_sign, uint8_t *sig, uint8_t *pby,
                int (*is_canonical)(uint8_t by, uint8_t sig[64])) {
  if (node->curve->params) {
    return ecdsa_sign(node->curve->params, hasher_sign, node->private_key, msg,
                      msg_len, sig, pby, is_canonical);
  } else if (node->curve == &curve25519_info) {
    return 1;  // signatures are not supported
  } else {
    hdnode_fill_public_key(node);
    if (node->curve == &ed25519_info) {
      ed25519_sign(msg, msg_len, node->private_key, node->public_key + 1, sig);
    } else if (node->curve == &ed25519_sha3_info) {
      ed25519_sign_sha3(msg, msg_len, node->private_key, node->public_key + 1,
                        sig);
#if USE_KECCAK
    } else if (node->curve == &ed25519_keccak_info) {
      ed25519_sign_keccak(msg, msg_len, node->private_key, node->public_key + 1,
                          sig);
#endif
    }
    return 0;
  }
}

int hdnode_sign_digest(HDNode *node, const uint8_t *digest, uint8_t *sig,
                       uint8_t *pby,
                       int (*is_canonical)(uint8_t by, uint8_t sig[64])) {
  if (node->curve->params) {
    return ecdsa_sign_digest(node->curve->params, node->private_key, digest,
                             sig, pby, is_canonical);
  } else if (node->curve == &curve25519_info) {
    return 1;  // signatures are not supported
  } else {
    return hdnode_sign(node, digest, 32, 0, sig, pby, is_canonical);
  }
}

int hdnode_get_shared_key(const HDNode *node, const uint8_t *peer_public_key,
                          uint8_t *session_key, int *result_size) {
  // Use elliptic curve Diffie-Helman to compute shared session key
  if (node->curve->params) {
    if (ecdh_multiply(node->curve->params, node->private_key, peer_public_key,
                      session_key) != 0) {
      return 1;
    }
    *result_size = 65;
    return 0;
  } else if (node->curve == &curve25519_info) {
    session_key[0] = 0x04;
    if (peer_public_key[0] != 0x40) {
      return 1;  // Curve25519 public key should start with 0x40 byte.
    }
    curve25519_scalarmult(session_key + 1, node->private_key,
                          peer_public_key + 1);
    *result_size = 33;
    return 0;
  } else {
    *result_size = 0;
    return 1;  // ECDH is not supported
  }
}

static int hdnode_serialize(const HDNode *node, uint32_t fingerprint,
                            uint32_t version, char use_public, char *str,
                            int strsize) {
  uint8_t node_data[78];
  write_be(node_data, version);
  node_data[4] = node->depth;
  write_be(node_data + 5, fingerprint);
  write_be(node_data + 9, node->child_num);
  memcpy(node_data + 13, node->chain_code, 32);
  if (use_public) {
    memcpy(node_data + 45, node->public_key, 33);
  } else {
    node_data[45] = 0;
    memcpy(node_data + 46, node->private_key, 32);
  }
  int ret = base58_encode_check(node_data, sizeof(node_data),
                                node->curve->hasher_base58, str, strsize);
  memzero(node_data, sizeof(node_data));
  return ret;
}

int hdnode_serialize_public(const HDNode *node, uint32_t fingerprint,
                            uint32_t version, char *str, int strsize) {
  return hdnode_serialize(node, fingerprint, version, 1, str, strsize);
}

int hdnode_serialize_private(const HDNode *node, uint32_t fingerprint,
                             uint32_t version, char *str, int strsize) {
  return hdnode_serialize(node, fingerprint, version, 0, str, strsize);
}

// check for validity of curve point in case of public data not performed
int hdnode_deserialize(const char *str, uint32_t version_public,
                       uint32_t version_private, const char *curve,
                       HDNode *node, uint32_t *fingerprint) {
  uint8_t node_data[78];
  memzero(node, sizeof(HDNode));
  node->curve = get_curve_by_name(curve);
  if (base58_decode_check(str, node->curve->hasher_base58, node_data,
                          sizeof(node_data)) != sizeof(node_data)) {
    return -1;
  }
  uint32_t version = read_be(node_data);
  if (version == version_public) {
    memzero(node->private_key, sizeof(node->private_key));
    memcpy(node->public_key, node_data + 45, 33);
  } else if (version == version_private) {  // private node
    if (node_data[45]) {                    // invalid data
      return -2;
    }
    memcpy(node->private_key, node_data + 46, 32);
    memzero(node->public_key, sizeof(node->public_key));
  } else {
    return -3;  // invalid version
  }
  node->depth = node_data[4];
  if (fingerprint) {
    *fingerprint = read_be(node_data + 5);
  }
  node->child_num = read_be(node_data + 9);
  memcpy(node->chain_code, node_data + 13, 32);
  return 0;
}

const curve_info *get_curve_by_name(const char *curve_name) {
  if (curve_name == 0) {
    return 0;
  }
  if (strcmp(curve_name, SECP256K1_NAME) == 0) {
    return &secp256k1_info;
  }
  if (strcmp(curve_name, SECP256K1_DECRED_NAME) == 0) {
    return &secp256k1_decred_info;
  }
  if (strcmp(curve_name, SECP256K1_GROESTL_NAME) == 0) {
    return &secp256k1_groestl_info;
  }
  if (strcmp(curve_name, SECP256K1_SMART_NAME) == 0) {
    return &secp256k1_smart_info;
  }
  if (strcmp(curve_name, NIST256P1_NAME) == 0) {
    return &nist256p1_info;
  }
  if (strcmp(curve_name, ED25519_NAME) == 0) {
    return &ed25519_info;
  }
  if (strcmp(curve_name, ED25519_CARDANO_NAME) == 0) {
    return &ed25519_cardano_info;
  }
  if (strcmp(curve_name, ED25519_SHA3_NAME) == 0) {
    return &ed25519_sha3_info;
  }
#if USE_KECCAK
  if (strcmp(curve_name, ED25519_KECCAK_NAME) == 0) {
    return &ed25519_keccak_info;
  }
#endif
  if (strcmp(curve_name, CURVE25519_NAME) == 0) {
    return &curve25519_info;
  }
  return 0;
}