r1

src/bip38.cpp

@@ -0,0 +1,279 @@
+// Copyright (c) 2017-2018 The PIVX developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include "bip38.h"
+#include "base58.h"
+#include "hash.h"
+#include "pubkey.h"
+#include "util.h"
+#include "utilstrencodings.h"
+#include "random.h"
+
+#include <openssl/aes.h>
+#include <openssl/sha.h>
+#include <secp256k1.h>
+#include <string>
+
+
+/** 39 bytes - 78 characters
+ * 1) Prefix - 2 bytes - 4 chars - strKey[0..3]
+ * 2) Flagbyte - 1 byte - 2 chars - strKey[4..5]
+ * 3) addresshash - 4 bytes - 8 chars - strKey[6..13]
+ * 4) Owner Entropy - 8 bytes - 16 chars - strKey[14..29]
+ * 5) Encrypted Part 1 - 8 bytes - 16 chars - strKey[30..45]
+ * 6) Encrypted Part 2 - 16 bytes - 32 chars - strKey[46..77]
+ */
+
+void DecryptAES(uint256 encryptedIn, uint256 decryptionKey, uint256& output)
+{
+    AES_KEY key;
+    AES_set_decrypt_key(decryptionKey.begin(), 256, &key);
+    AES_decrypt(encryptedIn.begin(), output.begin(), &key);
+}
+
+void ComputePreFactor(std::string strPassphrase, std::string strSalt, uint256& prefactor)
+{
+    //passfactor is the scrypt hash of passphrase and ownersalt (NOTE this needs to handle alt cases too in the future)
+    uint64_t s = uint256(ReverseEndianString(strSalt)).Get64();
+    scrypt_hash(strPassphrase.c_str(), strPassphrase.size(), BEGIN(s), strSalt.size() / 2, BEGIN(prefactor), 16384, 8, 8, 32);
+}
+
+void ComputePassfactor(std::string ownersalt, uint256 prefactor, uint256& passfactor)
+{
+    //concat prefactor and ownersalt
+    uint512 temp(ReverseEndianString(HexStr(prefactor) + ownersalt));
+    Hash(temp.begin(), 40, passfactor.begin()); //40 bytes is the length of prefactor + salt
+    Hash(passfactor.begin(), 32, passfactor.begin());
+}
+
+bool ComputePasspoint(uint256 passfactor, CPubKey& passpoint)
+{
+    size_t clen = 65;
+    secp256k1_context *ctx = secp256k1_context_create(SECP256K1_CONTEXT_SIGN);
+    assert(ctx != nullptr);
+    {
+        // Pass in a random blinding seed to the secp256k1 context.
+        std::vector<unsigned char, secure_allocator<unsigned char>> vseed(32);
+        GetRandBytes(vseed.data(), 32);
+        bool ret = secp256k1_context_randomize(ctx, vseed.data());
+        assert(ret);
+    }
+    secp256k1_pubkey pubkey;
+
+    //passpoint is the ec_mult of passfactor on secp256k1
+    if (!secp256k1_ec_pubkey_create(ctx, &pubkey, passfactor.begin())) {
+        secp256k1_context_destroy(ctx);
+        return false;
+    }
+
+    secp256k1_ec_pubkey_serialize(ctx, (unsigned char*)passpoint.begin(), &clen, &pubkey, SECP256K1_EC_COMPRESSED);
+    secp256k1_context_destroy(ctx);
+
+    if (passpoint.size() != clen)
+        return false;
+
+    if (!passpoint.IsValid())
+        return false;
+
+    return true;
+}
+
+void ComputeSeedBPass(CPubKey passpoint, std::string strAddressHash, std::string strOwnerSalt, uint512& seedBPass)
+{
+    // Derive decryption key for seedb using scrypt with passpoint, addresshash, and ownerentropy
+    string salt = ReverseEndianString(strAddressHash + strOwnerSalt);
+    uint256 s2(salt);
+    scrypt_hash(BEGIN(passpoint), HexStr(passpoint).size() / 2, BEGIN(s2), salt.size() / 2, BEGIN(seedBPass), 1024, 1, 1, 64);
+}
+
+void ComputeFactorB(uint256 seedB, uint256& factorB)
+{
+    //factorB - a double sha256 hash of seedb
+    Hash(seedB.begin(), 24, factorB.begin()); //seedB is only 24 bytes
+    Hash(factorB.begin(), 32, factorB.begin());
+}
+
+std::string AddressToBip38Hash(std::string address)
+{
+    uint256 addrCheck;
+    Hash((void*)address.c_str(), address.size(), addrCheck.begin());
+    Hash(addrCheck.begin(), 32, addrCheck.begin());
+
+    return HexStr(addrCheck).substr(0, 8);
+}
+
+std::string BIP38_Encrypt(std::string strAddress, std::string strPassphrase, uint256 privKey, bool fCompressed)
+{
+    string strAddressHash = AddressToBip38Hash(strAddress);
+
+    uint512 hashed;
+    uint64_t salt = uint256(ReverseEndianString(strAddressHash)).Get64();
+    scrypt_hash(strPassphrase.c_str(), strPassphrase.size(), BEGIN(salt), strAddressHash.size() / 2, BEGIN(hashed), 16384, 8, 8, 64);
+
+    uint256 derivedHalf1(hashed.ToString().substr(64, 64));
+    uint256 derivedHalf2(hashed.ToString().substr(0, 64));
+
+    //block1 = (pointb[1...16] xor derivedhalf1[0...15])
+    uint256 block1 = uint256((privKey << 128) ^ (derivedHalf1 << 128)) >> 128;
+
+    //encrypt part 1
+    uint512 encrypted1;
+    AES_KEY key;
+    AES_set_encrypt_key(derivedHalf2.begin(), 256, &key);
+    AES_encrypt(block1.begin(), encrypted1.begin(), &key);
+
+    //block2 = (pointb[17...32] xor derivedhalf1[16...31]
+    uint256 p2 = privKey >> 128;
+    uint256 dh12 = derivedHalf1 >> 128;
+    uint256 block2 = uint256(p2 ^ dh12);
+
+    //encrypt part 2
+    uint512 encrypted2;
+    AES_encrypt(block2.begin(), encrypted2.begin(), &key);
+
+    string strPrefix = "0142";
+    strPrefix += (fCompressed ? "E0" : "C0");
+
+    uint512 encryptedKey(ReverseEndianString(strPrefix + strAddressHash));
+
+    //add encrypted1 to the end of encryptedKey
+    encryptedKey = encryptedKey | (encrypted1 << 56);
+
+    //add encrypted2 to the end of encryptedKey
+    encryptedKey = encryptedKey | (encrypted2 << (56 + 128));
+
+    //Base58 checksum is the 4 bytes of dSHA256 hash of the encrypted key
+    uint256 hashChecksum = Hash(encryptedKey.begin(), encryptedKey.begin() + 39);
+    uint512 b58Checksum(hashChecksum.ToString().substr(64 - 8, 8));
+
+    // append the encrypted key with checksum (currently occupies 312 bits)
+    encryptedKey = encryptedKey | (b58Checksum << 312);
+
+    //43 bytes is the total size that we are encoding
+    return EncodeBase58(encryptedKey.begin(), encryptedKey.begin() + 43);
+}
+
+bool BIP38_Decrypt(std::string strPassphrase, std::string strEncryptedKey, uint256& privKey, bool& fCompressed)
+{
+    std::string strKey = DecodeBase58(strEncryptedKey.c_str());
+
+    //incorrect encoding of key, it must be 39 bytes - and another 4 bytes for base58 checksum
+    if (strKey.size() != (78 + 8))
+        return false;
+
+    //invalid prefix
+    if (uint256(ReverseEndianString(strKey.substr(0, 2))) != uint256(0x01))
+        return false;
+
+    uint256 type(ReverseEndianString(strKey.substr(2, 2)));
+    uint256 flag(ReverseEndianString(strKey.substr(4, 2)));
+    std::string strAddressHash = strKey.substr(6, 8);
+    std::string ownersalt = strKey.substr(14, 16);
+    uint256 encryptedPart1(ReverseEndianString(strKey.substr(30, 16)));
+    uint256 encryptedPart2(ReverseEndianString(strKey.substr(46, 32)));
+
+    fCompressed = (flag & uint256(0x20)) != 0;
+
+    //not ec multiplied
+    if (type == uint256(0x42)) {
+        uint512 hashed;
+        encryptedPart1 = uint256(ReverseEndianString(strKey.substr(14, 32)));
+        uint64_t salt = uint256(ReverseEndianString(strAddressHash)).Get64();
+        scrypt_hash(strPassphrase.c_str(), strPassphrase.size(), BEGIN(salt), strAddressHash.size() / 2, BEGIN(hashed), 16384, 8, 8, 64);
+
+        uint256 derivedHalf1(hashed.ToString().substr(64, 64));
+        uint256 derivedHalf2(hashed.ToString().substr(0, 64));
+
+        uint256 decryptedPart1;
+        DecryptAES(encryptedPart1, derivedHalf2, decryptedPart1);
+
+        uint256 decryptedPart2;
+        DecryptAES(encryptedPart2, derivedHalf2, decryptedPart2);
+
+        //combine decrypted parts into 64 bytes
+        uint256 temp1 = decryptedPart2 << 128;
+        temp1 = temp1 | decryptedPart1;
+
+        //xor the decryption with the derived half 1 for the final key
+        privKey = temp1 ^ derivedHalf1;
+
+        return true;
+    } else if (type != uint256(0x43)) //invalid type
+        return false;
+
+    bool fLotSequence = (flag & 0x04) != 0;
+
+    std::string prefactorSalt = ownersalt;
+    if (fLotSequence)
+        prefactorSalt = ownersalt.substr(0, 8);
+
+    uint256 prefactor;
+    ComputePreFactor(strPassphrase, prefactorSalt, prefactor);
+
+    uint256 passfactor;
+    if (fLotSequence)
+        ComputePassfactor(ownersalt, prefactor, passfactor);
+    else
+        passfactor = prefactor;
+
+    CPubKey passpoint;
+    if (!ComputePasspoint(passfactor, passpoint))
+        return false;
+
+    uint512 seedBPass;
+    ComputeSeedBPass(passpoint, strAddressHash, ownersalt, seedBPass);
+
+    //get derived halfs, being mindful for endian switch
+    uint256 derivedHalf1(seedBPass.ToString().substr(64, 64));
+    uint256 derivedHalf2(seedBPass.ToString().substr(0, 64));
+
+    /** Decrypt encryptedpart2 using AES256Decrypt to yield the last 8 bytes of seedb and the last 8 bytes of encryptedpart1. **/
+    uint256 decryptedPart2;
+    DecryptAES(encryptedPart2, derivedHalf2, decryptedPart2);
+
+    //xor decryptedPart2 and 2nd half of derived half 1
+    uint256 x0 = derivedHalf1 >> 128; //drop off the first half (note: endian)
+    uint256 x1 = decryptedPart2 ^ x0;
+    uint256 seedbPart2 = x1 >> 64;
+
+    /** Decrypt encryptedpart1 to yield the remainder of seedb. **/
+    uint256 decryptedPart1;
+    uint256 x2 = x1 & uint256("0xffffffffffffffff"); // set x2 to seedbPart1 (still encrypted)
+    x2 = x2 << 64;                                   //make room to add encryptedPart1 to the front
+    x2 = encryptedPart1 | x2;                        //combine with encryptedPart1
+    DecryptAES(x2, derivedHalf2, decryptedPart1);
+
+    //decrypted part 1: seedb[0..15] xor derivedhalf1[0..15]
+    uint256 x3 = derivedHalf1 & uint256("0xffffffffffffffffffffffffffffffff");
+    uint256 seedbPart1 = decryptedPart1 ^ x3;
+    uint256 seedB = seedbPart1 | (seedbPart2 << 128);
+
+    uint256 factorB;
+    ComputeFactorB(seedB, factorB);
+
+    //multiply passfactor by factorb mod N to yield the priv key
+    secp256k1_context *ctx = secp256k1_context_create(SECP256K1_CONTEXT_SIGN);
+    assert(ctx != nullptr);
+    {
+        // Pass in a random blinding seed to the secp256k1 context.
+        std::vector<unsigned char, secure_allocator<unsigned char>> vseed(32);
+        GetRandBytes(vseed.data(), 32);
+        bool ret = secp256k1_context_randomize(ctx, vseed.data());
+        assert(ret);
+    }
+    privKey = factorB;
+    if (!secp256k1_ec_privkey_tweak_mul(ctx, privKey.begin(), passfactor.begin())) {
+        secp256k1_context_destroy(ctx);
+        return false;
+    }
+    secp256k1_context_destroy(ctx);
+
+    //double check that the address hash matches our final privkey
+    CKey k;
+    k.Set(privKey.begin(), privKey.end(), fCompressed);
+    CPubKey pubkey = k.GetPubKey();
+    string address = CBitcoinAddress(pubkey.GetID()).ToString();
+
+    return strAddressHash == AddressToBip38Hash(address);
+}