1 files changed, 593 insertions, 0 deletions
diff --git a/src/key.cpp b/src/key.cpp
new file mode 100644
index 0000000000..85dc9cda2b
--- /dev/null
+++ b/src/key.cpp
@@ -0,0 +1,593 @@
+// Copyright (c) 2009-2012 The Bitcoin developers
+// 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>
+
+#include "key.h"
+
+
+// anonymous namespace with local implementation code (OpenSSL interaction)
+namespace {
+
+// Generate a private key from just the secret parameter
+int EC_KEY_regenerate_key(EC_KEY *eckey, BIGNUM *priv_key)
+{
+    int ok = 0;
+    BN_CTX *ctx = NULL;
+    EC_POINT *pub_key = NULL;
+
+    if (!eckey) return 0;
+
+    const EC_GROUP *group = EC_KEY_get0_group(eckey);
+
+    if ((ctx = BN_CTX_new()) == NULL)
+        goto err;
+
+    pub_key = EC_POINT_new(group);
+
+    if (pub_key == NULL)
+        goto err;
+
+    if (!EC_POINT_mul(group, pub_key, priv_key, NULL, NULL, ctx))
+        goto err;
+
+    EC_KEY_set_private_key(eckey,priv_key);
+    EC_KEY_set_public_key(eckey,pub_key);
+
+    ok = 1;
+
+err:
+
+    if (pub_key)
+        EC_POINT_free(pub_key);
+    if (ctx != NULL)
+        BN_CTX_free(ctx);
+
+    return(ok);
+}
+
+// Perform ECDSA key recovery (see SEC1 4.1.6) for curves over (mod p)-fields
+// recid selects which key is recovered
+// if check is non-zero, additional checks are performed
+int ECDSA_SIG_recover_key_GFp(EC_KEY *eckey, ECDSA_SIG *ecsig, const unsigned char *msg, int msglen, int recid, int check)
+{
+    if (!eckey) return 0;
+
+    int ret = 0;
+    BN_CTX *ctx = NULL;
+
+    BIGNUM *x = NULL;
+    BIGNUM *e = NULL;
+    BIGNUM *order = NULL;
+    BIGNUM *sor = NULL;
+    BIGNUM *eor = NULL;
+    BIGNUM *field = NULL;
+    EC_POINT *R = NULL;
+    EC_POINT *O = NULL;
+    EC_POINT *Q = NULL;
+    BIGNUM *rr = NULL;
+    BIGNUM *zero = NULL;
+    int n = 0;
+    int i = recid / 2;
+
+    const EC_GROUP *group = EC_KEY_get0_group(eckey);
+    if ((ctx = BN_CTX_new()) == NULL) { ret = -1; goto err; }
+    BN_CTX_start(ctx);
+    order = BN_CTX_get(ctx);
+    if (!EC_GROUP_get_order(group, order, ctx)) { ret = -2; goto err; }
+    x = BN_CTX_get(ctx);
+    if (!BN_copy(x, order)) { ret=-1; goto err; }
+    if (!BN_mul_word(x, i)) { ret=-1; goto err; }
+    if (!BN_add(x, x, ecsig->r)) { ret=-1; goto err; }
+    field = BN_CTX_get(ctx);
+    if (!EC_GROUP_get_curve_GFp(group, field, NULL, NULL, ctx)) { ret=-2; goto err; }
+    if (BN_cmp(x, field) >= 0) { ret=0; goto err; }
+    if ((R = EC_POINT_new(group)) == NULL) { ret = -2; goto err; }
+    if (!EC_POINT_set_compressed_coordinates_GFp(group, R, x, recid % 2, ctx)) { ret=0; goto err; }
+    if (check)
+    {
+        if ((O = EC_POINT_new(group)) == NULL) { ret = -2; goto err; }
+        if (!EC_POINT_mul(group, O, NULL, R, order, ctx)) { ret=-2; goto err; }
+        if (!EC_POINT_is_at_infinity(group, O)) { ret = 0; goto err; }
+    }
+    if ((Q = EC_POINT_new(group)) == NULL) { ret = -2; goto err; }
+    n = EC_GROUP_get_degree(group);
+    e = BN_CTX_get(ctx);
+    if (!BN_bin2bn(msg, msglen, e)) { ret=-1; goto err; }
+    if (8*msglen > n) BN_rshift(e, e, 8-(n & 7));
+    zero = BN_CTX_get(ctx);
+    if (!BN_zero(zero)) { ret=-1; goto err; }
+    if (!BN_mod_sub(e, zero, e, order, ctx)) { ret=-1; goto err; }
+    rr = BN_CTX_get(ctx);
+    if (!BN_mod_inverse(rr, ecsig->r, order, ctx)) { ret=-1; goto err; }
+    sor = BN_CTX_get(ctx);
+    if (!BN_mod_mul(sor, ecsig->s, rr, order, ctx)) { ret=-1; goto err; }
+    eor = BN_CTX_get(ctx);
+    if (!BN_mod_mul(eor, e, rr, order, ctx)) { ret=-1; goto err; }
+    if (!EC_POINT_mul(group, Q, eor, R, sor, ctx)) { ret=-2; goto err; }
+    if (!EC_KEY_set_public_key(eckey, Q)) { ret=-2; goto err; }
+
+    ret = 1;
+
+err:
+    if (ctx) {
+        BN_CTX_end(ctx);
+        BN_CTX_free(ctx);
+    }
+    if (R != NULL) EC_POINT_free(R);
+    if (O != NULL) EC_POINT_free(O);
+    if (Q != NULL) EC_POINT_free(Q);
+    return ret;
+}
+
+// RAII Wrapper around OpenSSL's EC_KEY
+class CECKey {
+private:
+    EC_KEY *pkey;
+
+public:
+    CECKey() {
+        pkey = EC_KEY_new_by_curve_name(NID_secp256k1);
+        assert(pkey != NULL);
+    }
+
+    ~CECKey() {
+        EC_KEY_free(pkey);
+    }
+
+    void GetSecretBytes(unsigned char vch[32]) const {
+        const BIGNUM *bn = EC_KEY_get0_private_key(pkey);
+        assert(bn);
+        int nBytes = BN_num_bytes(bn);
+        int n=BN_bn2bin(bn,&vch[32 - nBytes]);
+        assert(n == nBytes);
+        memset(vch, 0, 32 - nBytes);
+    }
+
+    void SetSecretBytes(const unsigned char vch[32]) {
+        BIGNUM bn;
+        BN_init(&bn);
+        assert(BN_bin2bn(vch, 32, &bn));
+        assert(EC_KEY_regenerate_key(pkey, &bn));
+        BN_clear_free(&bn);
+    }
+
+    void GetPrivKey(CPrivKey &privkey, bool fCompressed) {
+        EC_KEY_set_conv_form(pkey, fCompressed ? POINT_CONVERSION_COMPRESSED : POINT_CONVERSION_UNCOMPRESSED);
+        int nSize = i2d_ECPrivateKey(pkey, NULL);
+        assert(nSize);
+        privkey.resize(nSize);
+        unsigned char* pbegin = &privkey[0];
+        int nSize2 = i2d_ECPrivateKey(pkey, &pbegin);
+        assert(nSize == nSize2);
+    }
+
+    bool SetPrivKey(const CPrivKey &privkey) {
+        const unsigned char* pbegin = &privkey[0];
+        if (d2i_ECPrivateKey(&pkey, &pbegin, privkey.size())) {
+            // d2i_ECPrivateKey returns true if parsing succeeds.
+            // This doesn't necessarily mean the key is valid.
+            if (EC_KEY_check_key(pkey))
+                return true;
+        }
+        return false;
+    }
+
+    void GetPubKey(CPubKey &pubkey, bool fCompressed) {
+        EC_KEY_set_conv_form(pkey, fCompressed ? POINT_CONVERSION_COMPRESSED : POINT_CONVERSION_UNCOMPRESSED);
+        int nSize = i2o_ECPublicKey(pkey, NULL);
+        assert(nSize);
+        assert(nSize <= 65);
+        unsigned char c[65];
+        unsigned char *pbegin = c;
+        int nSize2 = i2o_ECPublicKey(pkey, &pbegin);
+        assert(nSize == nSize2);
+        pubkey.Set(&c[0], &c[nSize]);
+    }
+
+    bool SetPubKey(const CPubKey &pubkey) {
+        const unsigned char* pbegin = pubkey.begin();
+        return o2i_ECPublicKey(&pkey, &pbegin, pubkey.size());
+    }
+
+    bool Sign(const uint256 &hash, std::vector<unsigned char>& vchSig) {
+        vchSig.clear();
+        ECDSA_SIG *sig = ECDSA_do_sign((unsigned char*)&hash, sizeof(hash), pkey);
+        if (sig == NULL)
+            return false;
+        if (BN_is_odd(sig->s)) {
+            // enforce even S values, by negating the value (modulo the order) if odd
+            BN_CTX *ctx = BN_CTX_new();
+            BN_CTX_start(ctx);
+            const EC_GROUP *group = EC_KEY_get0_group(pkey);
+            BIGNUM *order = BN_CTX_get(ctx);
+            EC_GROUP_get_order(group, order, ctx);
+            BN_sub(sig->s, order, sig->s);
+            BN_CTX_end(ctx);
+            BN_CTX_free(ctx);
+        }
+        unsigned int nSize = ECDSA_size(pkey);
+        vchSig.resize(nSize); // Make sure it is big enough
+        unsigned char *pos = &vchSig[0];
+        nSize = i2d_ECDSA_SIG(sig, &pos);
+        ECDSA_SIG_free(sig);
+        vchSig.resize(nSize); // Shrink to fit actual size
+        return true;
+    }
+
+    bool Verify(const uint256 &hash, const std::vector<unsigned char>& vchSig) {
+        // -1 = error, 0 = bad sig, 1 = good
+        if (ECDSA_verify(0, (unsigned char*)&hash, sizeof(hash), &vchSig[0], vchSig.size(), pkey) != 1)
+            return false;
+        return true;
+    }
+
+    bool SignCompact(const uint256 &hash, unsigned char *p64, int &rec) {
+        bool fOk = false;
+        ECDSA_SIG *sig = ECDSA_do_sign((unsigned char*)&hash, sizeof(hash), pkey);
+        if (sig==NULL)
+            return false;
+        memset(p64, 0, 64);
+        int nBitsR = BN_num_bits(sig->r);
+        int nBitsS = BN_num_bits(sig->s);
+        if (nBitsR <= 256 && nBitsS <= 256) {
+            CPubKey pubkey;
+            GetPubKey(pubkey, true);
+            for (int i=0; i<4; i++) {
+                CECKey keyRec;
+                if (ECDSA_SIG_recover_key_GFp(keyRec.pkey, sig, (unsigned char*)&hash, sizeof(hash), i, 1) == 1) {
+                    CPubKey pubkeyRec;
+                    keyRec.GetPubKey(pubkeyRec, true);
+                    if (pubkeyRec == pubkey) {
+                        rec = i;
+                        fOk = true;
+                        break;
+                    }
+                }
+            }
+            assert(fOk);
+            BN_bn2bin(sig->r,&p64[32-(nBitsR+7)/8]);
+            BN_bn2bin(sig->s,&p64[64-(nBitsS+7)/8]);
+        }
+        ECDSA_SIG_free(sig);
+        return fOk;
+    }
+
+    // reconstruct public key from a compact signature
+    // This is only slightly more CPU intensive than just verifying it.
+    // If this function succeeds, the recovered public key is guaranteed to be valid
+    // (the signature is a valid signature of the given data for that key)
+    bool Recover(const uint256 &hash, const unsigned char *p64, int rec)
+    {
+        if (rec<0 || rec>=3)
+            return false;
+        ECDSA_SIG *sig = ECDSA_SIG_new();
+        BN_bin2bn(&p64[0],  32, sig->r);
+        BN_bin2bn(&p64[32], 32, sig->s);
+        bool ret = ECDSA_SIG_recover_key_GFp(pkey, sig, (unsigned char*)&hash, sizeof(hash), rec, 0) == 1;
+        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
+
+bool CKey::Check(const unsigned char *vch) {
+    // Do not convert to OpenSSL's data structures for range-checking keys,
+    // it's easy enough to do directly.
+    static const unsigned char vchMax[32] = {
+        0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,
+        0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFE,
+        0xBA,0xAE,0xDC,0xE6,0xAF,0x48,0xA0,0x3B,
+        0xBF,0xD2,0x5E,0x8C,0xD0,0x36,0x41,0x40
+    };
+    bool fIsZero = true;
+    for (int i=0; i<32 && fIsZero; i++)
+        if (vch[i] != 0)
+            fIsZero = false;
+    if (fIsZero)
+        return false;
+    for (int i=0; i<32; i++) {
+        if (vch[i] < vchMax[i])
+            return true;
+        if (vch[i] > vchMax[i])
+            return false;
+    }
+    return true;
+}
+
+void CKey::MakeNewKey(bool fCompressedIn) {
+    do {
+        RAND_bytes(vch, sizeof(vch));
+    } while (!Check(vch));
+    fValid = true;
+    fCompressed = fCompressedIn;
+}
+
+bool CKey::SetPrivKey(const CPrivKey &privkey, bool fCompressedIn) {
+    CECKey key;
+    if (!key.SetPrivKey(privkey))
+        return false;
+    key.GetSecretBytes(vch);
+    fCompressed = fCompressedIn;
+    fValid = true;
+    return true;
+}
+
+CPrivKey CKey::GetPrivKey() const {
+    assert(fValid);
+    CECKey key;
+    key.SetSecretBytes(vch);
+    CPrivKey privkey;
+    key.GetPrivKey(privkey, fCompressed);
+    return privkey;
+}
+
+CPubKey CKey::GetPubKey() const {
+    assert(fValid);
+    CECKey key;
+    key.SetSecretBytes(vch);
+    CPubKey pubkey;
+    key.GetPubKey(pubkey, fCompressed);
+    return pubkey;
+}
+
+bool CKey::Sign(const uint256 &hash, std::vector<unsigned char>& vchSig) const {
+    if (!fValid)
+        return false;
+    CECKey key;
+    key.SetSecretBytes(vch);
+    return key.Sign(hash, vchSig);
+}
+
+bool CKey::SignCompact(const uint256 &hash, std::vector<unsigned char>& vchSig) const {
+    if (!fValid)
+        return false;
+    CECKey key;
+    key.SetSecretBytes(vch);
+    vchSig.resize(65);
+    int rec = -1;
+    if (!key.SignCompact(hash, &vchSig[1], rec))
+        return false;
+    assert(rec != -1);
+    vchSig[0] = 27 + rec + (fCompressed ? 4 : 0);
+    return true;
+}
+
+bool CPubKey::Verify(const uint256 &hash, const std::vector<unsigned char>& vchSig) const {
+    if (!IsValid())
+        return false;
+    CECKey key;
+    if (!key.SetPubKey(*this))
+        return false;
+    if (!key.Verify(hash, vchSig))
+        return false;
+    return true;
+}
+
+bool CPubKey::RecoverCompact(const uint256 &hash, const std::vector<unsigned char>& vchSig) {
+    if (vchSig.size() != 65)
+        return false;
+    CECKey key;
+    if (!key.Recover(hash, &vchSig[1], (vchSig[0] - 27) & ~4))
+        return false;
+    key.GetPubKey(*this, (vchSig[0] - 27) & 4);
+    return true;
+}
+
+bool CPubKey::VerifyCompact(const uint256 &hash, const std::vector<unsigned char>& vchSig) const {
+    if (!IsValid())
+        return false;
+    if (vchSig.size() != 65)
+        return false;
+    CECKey key;
+    if (!key.Recover(hash, &vchSig[1], (vchSig[0] - 27) & ~4))
+        return false;
+    CPubKey pubkeyRec;
+    key.GetPubKey(pubkeyRec, IsCompressed());
+    if (*this != pubkeyRec)
+        return false;
+    return true;
+}
+
+bool CPubKey::IsFullyValid() const {
+    if (!IsValid())
+        return false;
+    CECKey key;
+    if (!key.SetPubKey(*this))
+        return false;
+    return true;
+}
+
+bool CPubKey::Decompress() {
+    if (!IsValid())
+        return false;
+    CECKey key;
+    if (!key.SetPubKey(*this))
+        return false;
+    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);
+}