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Merge pull request #2829 from sipa/bip32

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BIP 32 derivation + test vectors
This commit is contained in:
Gavin Andresen
2013-08-15 16:40:03 -07:00
parent 4323bfeafd a59db19ee3
commit 13d3b1c144
9 changed files with 585 additions and 36 deletions
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180
src/key.cpp
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@@ -2,6 +2,7 @@
// Distributed under the MIT/X11 software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
#include <openssl/bn.h>
#include <openssl/ecdsa.h>
#include <openssl/rand.h>
#include <openssl/obj_mac.h>
@@ -254,6 +255,57 @@ public:
ECDSA_SIG_free(sig);
return ret;
}
static bool TweakSecret(unsigned char vchSecretOut[32], const unsigned char vchSecretIn[32], const unsigned char vchTweak[32])
{
bool ret = true;
BN_CTX *ctx = BN_CTX_new();
BN_CTX_start(ctx);
BIGNUM *bnSecret = BN_CTX_get(ctx);
BIGNUM *bnTweak = BN_CTX_get(ctx);
BIGNUM *bnOrder = BN_CTX_get(ctx);
EC_GROUP *group = EC_GROUP_new_by_curve_name(NID_secp256k1);
EC_GROUP_get_order(group, bnOrder, ctx); // what a grossly inefficient way to get the (constant) group order...
BN_bin2bn(vchTweak, 32, bnTweak);
if (BN_cmp(bnTweak, bnOrder) >= 0)
ret = false; // extremely unlikely
BN_bin2bn(vchSecretIn, 32, bnSecret);
BN_add(bnSecret, bnSecret, bnTweak);
BN_nnmod(bnSecret, bnSecret, bnOrder, ctx);
if (BN_is_zero(bnSecret))
ret = false; // ridiculously unlikely
int nBits = BN_num_bits(bnSecret);
memset(vchSecretOut, 0, 32);
BN_bn2bin(bnSecret, &vchSecretOut[32-(nBits+7)/8]);
EC_GROUP_free(group);
BN_CTX_end(ctx);
BN_CTX_free(ctx);
return ret;
}
bool TweakPublic(const unsigned char vchTweak[32]) {
bool ret = true;
BN_CTX *ctx = BN_CTX_new();
BN_CTX_start(ctx);
BIGNUM *bnTweak = BN_CTX_get(ctx);
BIGNUM *bnOrder = BN_CTX_get(ctx);
BIGNUM *bnOne = BN_CTX_get(ctx);
const EC_GROUP *group = EC_KEY_get0_group(pkey);
EC_GROUP_get_order(group, bnOrder, ctx); // what a grossly inefficient way to get the (constant) group order...
BN_bin2bn(vchTweak, 32, bnTweak);
if (BN_cmp(bnTweak, bnOrder) >= 0)
ret = false; // extremely unlikely
EC_POINT *point = EC_POINT_dup(EC_KEY_get0_public_key(pkey), group);
BN_one(bnOne);
EC_POINT_mul(group, point, bnTweak, point, bnOne, ctx);
if (EC_POINT_is_at_infinity(group, point))
ret = false; // ridiculously unlikely
EC_KEY_set_public_key(pkey, point);
EC_POINT_free(point);
BN_CTX_end(ctx);
BN_CTX_free(ctx);
return ret;
}
};
}; // end of anonymous namespace
@@ -394,3 +446,131 @@ bool CPubKey::Decompress() {
key.GetPubKey(*this, false);
return true;
}
void static BIP32Hash(const unsigned char chainCode[32], unsigned int nChild, unsigned char header, const unsigned char data[32], unsigned char output[64]) {
unsigned char num[4];
num[0] = (nChild >> 24) & 0xFF;
num[1] = (nChild >> 16) & 0xFF;
num[2] = (nChild >> 8) & 0xFF;
num[3] = (nChild >> 0) & 0xFF;
HMAC_SHA512_CTX ctx;
HMAC_SHA512_Init(&ctx, chainCode, 32);
HMAC_SHA512_Update(&ctx, &header, 1);
HMAC_SHA512_Update(&ctx, data, 32);
HMAC_SHA512_Update(&ctx, num, 4);
HMAC_SHA512_Final(output, &ctx);
}
bool CKey::Derive(CKey& keyChild, unsigned char ccChild[32], unsigned int nChild, const unsigned char cc[32]) const {
assert(IsValid());
assert(IsCompressed());
unsigned char out[64];
LockObject(out);
if ((nChild >> 31) == 0) {
CPubKey pubkey = GetPubKey();
assert(pubkey.begin() + 33 == pubkey.end());
BIP32Hash(cc, nChild, *pubkey.begin(), pubkey.begin()+1, out);
} else {
assert(begin() + 32 == end());
BIP32Hash(cc, nChild, 0, begin(), out);
}
memcpy(ccChild, out+32, 32);
bool ret = CECKey::TweakSecret((unsigned char*)keyChild.begin(), begin(), out);
UnlockObject(out);
keyChild.fCompressed = true;
keyChild.fValid = ret;
return ret;
}
bool CPubKey::Derive(CPubKey& pubkeyChild, unsigned char ccChild[32], unsigned int nChild, const unsigned char cc[32]) const {
assert(IsValid());
assert((nChild >> 31) == 0);
assert(begin() + 33 == end());
unsigned char out[64];
BIP32Hash(cc, nChild, *begin(), begin()+1, out);
memcpy(ccChild, out+32, 32);
CECKey key;
bool ret = key.SetPubKey(*this);
ret &= key.TweakPublic(out);
key.GetPubKey(pubkeyChild, true);
return ret;
}
bool CExtKey::Derive(CExtKey &out, unsigned int nChild) const {
out.nDepth = nDepth + 1;
CKeyID id = key.GetPubKey().GetID();
memcpy(&out.vchFingerprint[0], &id, 4);
out.nChild = nChild;
return key.Derive(out.key, out.vchChainCode, nChild, vchChainCode);
}
void CExtKey::SetMaster(const unsigned char *seed, unsigned int nSeedLen) {
static const char hashkey[] = {'B','i','t','c','o','i','n',' ','s','e','e','d'};
HMAC_SHA512_CTX ctx;
HMAC_SHA512_Init(&ctx, hashkey, sizeof(hashkey));
HMAC_SHA512_Update(&ctx, seed, nSeedLen);
unsigned char out[64];
LockObject(out);
HMAC_SHA512_Final(out, &ctx);
key.Set(&out[0], &out[32], true);
memcpy(vchChainCode, &out[32], 32);
UnlockObject(out);
nDepth = 0;
nChild = 0;
memset(vchFingerprint, 0, sizeof(vchFingerprint));
}
CExtPubKey CExtKey::Neuter() const {
CExtPubKey ret;
ret.nDepth = nDepth;
memcpy(&ret.vchFingerprint[0], &vchFingerprint[0], 4);
ret.nChild = nChild;
ret.pubkey = key.GetPubKey();
memcpy(&ret.vchChainCode[0], &vchChainCode[0], 32);
return ret;
}
void CExtKey::Encode(unsigned char code[74]) const {
code[0] = nDepth;
memcpy(code+1, vchFingerprint, 4);
code[5] = (nChild >> 24) & 0xFF; code[6] = (nChild >> 16) & 0xFF;
code[7] = (nChild >> 8) & 0xFF; code[8] = (nChild >> 0) & 0xFF;
memcpy(code+9, vchChainCode, 32);
code[41] = 0;
assert(key.size() == 32);
memcpy(code+42, key.begin(), 32);
}
void CExtKey::Decode(const unsigned char code[74]) {
nDepth = code[0];
memcpy(vchFingerprint, code+1, 4);
nChild = (code[5] << 24) | (code[6] << 16) | (code[7] << 8) | code[8];
memcpy(vchChainCode, code+9, 32);
key.Set(code+42, code+74, true);
}
void CExtPubKey::Encode(unsigned char code[74]) const {
code[0] = nDepth;
memcpy(code+1, vchFingerprint, 4);
code[5] = (nChild >> 24) & 0xFF; code[6] = (nChild >> 16) & 0xFF;
code[7] = (nChild >> 8) & 0xFF; code[8] = (nChild >> 0) & 0xFF;
memcpy(code+9, vchChainCode, 32);
assert(pubkey.size() == 33);
memcpy(code+41, pubkey.begin(), 33);
}
void CExtPubKey::Decode(const unsigned char code[74]) {
nDepth = code[0];
memcpy(vchFingerprint, code+1, 4);
nChild = (code[5] << 24) | (code[6] << 16) | (code[7] << 8) | code[8];
memcpy(vchChainCode, code+9, 32);
pubkey.Set(code+41, code+74);
}
bool CExtPubKey::Derive(CExtPubKey &out, unsigned int nChild) const {
out.nDepth = nDepth + 1;
CKeyID id = pubkey.GetID();
memcpy(&out.vchFingerprint[0], &id, 4);
out.nChild = nChild;
return pubkey.Derive(out.pubkey, out.vchChainCode, nChild, vchChainCode);
}