1 files changed, 366 insertions, 0 deletions

diff --git a/src/bip32.cpp b/src/bip32.cpp
new file mode 100644
index 0000000..6423974
--- /dev/null
+++ b/src/bip32.cpp
@@ -0,0 +1,366 @@
+// Copyright (c) 2026 Bitflash developers
+// Distributed under the MIT/X11 software license.
+
+#include "bip32.h"
+#include "bip39_english.h"
+
+#include <openssl/bn.h>
+#include <openssl/crypto.h>
+#include <openssl/ec.h>
+#include <openssl/evp.h>
+#include <openssl/hmac.h>
+#include <openssl/obj_mac.h>
+#include <openssl/rand.h>
+#include <openssl/sha.h>
+
+#include <algorithm>
+#include <cctype>
+#include <cstring>
+#include <map>
+#include <sstream>
+
+namespace bitflash
+{
+
+static bool IsSupportedEntropySize(size_t n)
+{
+    return n == 16 || n == 20 || n == 24 || n == 28 || n == 32;
+}
+
+static bool GetBit(const unsigned char* data, size_t bit)
+{
+    return (data[bit / 8] >> (7 - (bit % 8))) & 1;
+}
+
+static void AppendBits(std::vector<bool>& out, const unsigned char* data,
+                       size_t nBits)
+{
+    for (size_t i = 0; i < nBits; i++)
+        out.push_back(GetBit(data, i));
+}
+
+static std::string NormalizeMnemonic(const std::string& in)
+{
+    std::string out;
+    bool inSpace = true;
+    for (unsigned char c : in)
+    {
+        if (std::isspace(c))
+        {
+            if (!inSpace)
+                out.push_back(' ');
+            inSpace = true;
+        }
+        else
+        {
+            out.push_back((char)std::tolower(c));
+            inSpace = false;
+        }
+    }
+    if (!out.empty() && out.back() == ' ')
+        out.pop_back();
+    return out;
+}
+
+static std::vector<std::string> SplitWords(const std::string& phrase)
+{
+    std::vector<std::string> words;
+    std::istringstream in(phrase);
+    std::string word;
+    while (in >> word)
+        words.push_back(word);
+    return words;
+}
+
+static const std::map<std::string, int>& WordIndex()
+{
+    static std::map<std::string, int> m;
+    if (m.empty())
+    {
+        for (int i = 0; i < 2048; i++)
+            m[BIP39_ENGLISH_WORDS[i]] = i;
+    }
+    return m;
+}
+
+static bool IsValidPrivateKey(const std::vector<unsigned char>& key)
+{
+    if (key.size() != 32)
+        return false;
+    bool fNonZero = false;
+    for (unsigned char c : key)
+        fNonZero = fNonZero || c != 0;
+    if (!fNonZero)
+        return false;
+
+    bool ok = false;
+    BIGNUM* bn = BN_bin2bn(&key[0], 32, NULL);
+    BIGNUM* order = BN_new();
+    EC_GROUP* group = EC_GROUP_new_by_curve_name(NID_secp256k1);
+    if (bn && order && group && EC_GROUP_get_order(group, order, NULL))
+        ok = BN_cmp(bn, order) < 0;
+    BN_free(bn);
+    BN_free(order);
+    EC_GROUP_free(group);
+    return ok;
+}
+
+static bool HmacSha512(const unsigned char* key, int keyLen,
+                       const unsigned char* data, size_t dataLen,
+                       unsigned char out[64])
+{
+    unsigned int len = 64;
+    return HMAC(EVP_sha512(), key, keyLen, data, dataLen, out, &len) != NULL &&
+           len == 64;
+}
+
+bool BIP39EntropyToMnemonic(const std::vector<unsigned char>& entropy,
+                            std::string& mnemonicOut,
+                            std::string& errorOut)
+{
+    mnemonicOut.clear();
+    errorOut.clear();
+    if (!IsSupportedEntropySize(entropy.size()))
+    {
+        errorOut = "entropy must be 128, 160, 192, 224, or 256 bits";
+        return false;
+    }
+
+    unsigned char checksum[SHA256_DIGEST_LENGTH];
+    SHA256(&entropy[0], entropy.size(), checksum);
+
+    const size_t entropyBits = entropy.size() * 8;
+    const size_t checksumBits = entropyBits / 32;
+
+    std::vector<bool> bits;
+    bits.reserve(entropyBits + checksumBits);
+    AppendBits(bits, &entropy[0], entropyBits);
+    AppendBits(bits, checksum, checksumBits);
+
+    const size_t words = bits.size() / 11;
+    for (size_t i = 0; i < words; i++)
+    {
+        int idx = 0;
+        for (int j = 0; j < 11; j++)
+            idx = (idx << 1) | (bits[i * 11 + j] ? 1 : 0);
+        if (i != 0)
+            mnemonicOut += " ";
+        mnemonicOut += BIP39_ENGLISH_WORDS[idx];
+    }
+    return true;
+}
+
+bool BIP39GenerateMnemonic(std::string& mnemonicOut,
+                           std::string& errorOut,
+                           unsigned int entropyBytes)
+{
+    mnemonicOut.clear();
+    errorOut.clear();
+    if (!IsSupportedEntropySize(entropyBytes))
+    {
+        errorOut = "entropy must be 16, 20, 24, 28, or 32 bytes";
+        return false;
+    }
+
+    std::vector<unsigned char> entropy(entropyBytes);
+    if (RAND_bytes(&entropy[0], entropy.size()) != 1)
+    {
+        errorOut = "RAND_bytes failed";
+        return false;
+    }
+    bool ok = BIP39EntropyToMnemonic(entropy, mnemonicOut, errorOut);
+    OPENSSL_cleanse(&entropy[0], entropy.size());
+    return ok;
+}
+
+bool BIP39ValidateMnemonic(const std::string& mnemonic,
+                           std::string& normalizedOut,
+                           std::string& errorOut)
+{
+    normalizedOut = NormalizeMnemonic(mnemonic);
+    errorOut.clear();
+    std::vector<std::string> words = SplitWords(normalizedOut);
+    const size_t nWords = words.size();
+    if (nWords != 12 && nWords != 15 && nWords != 18 && nWords != 21 && nWords != 24)
+    {
+        errorOut = "mnemonic must contain 12, 15, 18, 21, or 24 words";
+        return false;
+    }
+
+    const std::map<std::string, int>& index = WordIndex();
+    std::vector<bool> bits;
+    bits.reserve(nWords * 11);
+    for (const std::string& word : words)
+    {
+        std::map<std::string, int>::const_iterator mi = index.find(word);
+        if (mi == index.end())
+        {
+            errorOut = "mnemonic contains a word outside the BIP39 English list";
+            return false;
+        }
+        int value = mi->second;
+        for (int i = 10; i >= 0; i--)
+            bits.push_back(((value >> i) & 1) != 0);
+    }
+
+    const size_t totalBits = bits.size();
+    const size_t entropyBits = totalBits * 32 / 33;
+    const size_t checksumBits = totalBits - entropyBits;
+    std::vector<unsigned char> entropy(entropyBits / 8, 0);
+    for (size_t i = 0; i < entropyBits; i++)
+        if (bits[i])
+            entropy[i / 8] |= (unsigned char)(1 << (7 - (i % 8)));
+
+    unsigned char checksum[SHA256_DIGEST_LENGTH];
+    SHA256(&entropy[0], entropy.size(), checksum);
+    for (size_t i = 0; i < checksumBits; i++)
+    {
+        if (bits[entropyBits + i] != GetBit(checksum, i))
+        {
+            errorOut = "mnemonic checksum failed";
+            return false;
+        }
+    }
+    return true;
+}
+
+bool BIP39MnemonicToSeed(const std::string& mnemonic,
+                         const std::string& passphrase,
+                         std::vector<unsigned char>& seedOut,
+                         std::string& errorOut)
+{
+    seedOut.assign(64, 0);
+    std::string normalized;
+    if (!BIP39ValidateMnemonic(mnemonic, normalized, errorOut))
+    {
+        seedOut.clear();
+        return false;
+    }
+
+    const std::string salt = "mnemonic" + passphrase;
+    if (!PKCS5_PBKDF2_HMAC(normalized.c_str(), normalized.size(),
+                           (const unsigned char*)salt.data(), salt.size(),
+                           2048, EVP_sha512(), 64, &seedOut[0]))
+    {
+        seedOut.clear();
+        errorOut = "PBKDF2-HMAC-SHA512 failed";
+        return false;
+    }
+    return true;
+}
+
+bool BIP32MasterFromSeed(const std::vector<unsigned char>& seed,
+                         BIP32PrivateNode& nodeOut,
+                         std::string& errorOut)
+{
+    nodeOut.privateKey.clear();
+    nodeOut.chainCode.clear();
+    errorOut.clear();
+    if (seed.size() < 16 || seed.size() > 64)
+    {
+        errorOut = "BIP32 seed must be between 128 and 512 bits";
+        return false;
+    }
+
+    unsigned char I[64];
+    static const unsigned char key[] = "Bitcoin seed";
+    if (!HmacSha512(key, sizeof(key) - 1, &seed[0], seed.size(), I))
+    {
+        errorOut = "HMAC-SHA512 failed";
+        return false;
+    }
+
+    nodeOut.privateKey.assign(I, I + 32);
+    nodeOut.chainCode.assign(I + 32, I + 64);
+    OPENSSL_cleanse(I, sizeof(I));
+
+    if (!IsValidPrivateKey(nodeOut.privateKey))
+    {
+        nodeOut.privateKey.clear();
+        nodeOut.chainCode.clear();
+        errorOut = "BIP32 master key is invalid";
+        return false;
+    }
+    return true;
+}
+
+bool BIP32DeriveHardenedChild(const BIP32PrivateNode& parent,
+                              unsigned int childIndex,
+                              BIP32PrivateNode& childOut,
+                              std::string& errorOut)
+{
+    childOut.privateKey.clear();
+    childOut.chainCode.clear();
+    errorOut.clear();
+    if (!IsValidPrivateKey(parent.privateKey) || parent.chainCode.size() != 32)
+    {
+        errorOut = "parent private key or chain code is invalid";
+        return false;
+    }
+    if (childIndex >= 0x80000000U)
+    {
+        errorOut = "child index must be non-hardened; hardening is applied here";
+        return false;
+    }
+
+    const unsigned int hardened = childIndex | 0x80000000U;
+    unsigned char data[37];
+    data[0] = 0x00;
+    memcpy(data + 1, &parent.privateKey[0], 32);
+    data[33] = (unsigned char)((hardened >> 24) & 0xff);
+    data[34] = (unsigned char)((hardened >> 16) & 0xff);
+    data[35] = (unsigned char)((hardened >> 8) & 0xff);
+    data[36] = (unsigned char)(hardened & 0xff);
+
+    unsigned char I[64];
+    if (!HmacSha512(&parent.chainCode[0], 32, data, sizeof(data), I))
+    {
+        OPENSSL_cleanse(data, sizeof(data));
+        errorOut = "HMAC-SHA512 failed";
+        return false;
+    }
+    OPENSSL_cleanse(data, sizeof(data));
+
+    std::vector<unsigned char> IL(I, I + 32);
+    childOut.chainCode.assign(I + 32, I + 64);
+    OPENSSL_cleanse(I, sizeof(I));
+
+    BIGNUM* bnIL = BN_bin2bn(&IL[0], 32, NULL);
+    BIGNUM* bnParent = BN_bin2bn(&parent.privateKey[0], 32, NULL);
+    BIGNUM* bnOrder = BN_new();
+    BIGNUM* bnChild = BN_new();
+    BN_CTX* ctx = BN_CTX_new();
+    EC_GROUP* group = EC_GROUP_new_by_curve_name(NID_secp256k1);
+
+    bool ok = false;
+    if (bnIL && bnParent && bnOrder && bnChild && ctx && group &&
+        EC_GROUP_get_order(group, bnOrder, NULL) &&
+        BN_cmp(bnIL, bnOrder) < 0 &&
+        BN_mod_add(bnChild, bnIL, bnParent, bnOrder, ctx) &&
+        !BN_is_zero(bnChild))
+    {
+        childOut.privateKey.assign(32, 0);
+        int n = BN_num_bytes(bnChild);
+        BN_bn2bin(bnChild, &childOut.privateKey[32 - n]);
+        ok = true;
+    }
+
+    BN_free(bnIL);
+    BN_free(bnParent);
+    BN_free(bnOrder);
+    BN_free(bnChild);
+    BN_CTX_free(ctx);
+    EC_GROUP_free(group);
+    OPENSSL_cleanse(&IL[0], IL.size());
+
+    if (!ok)
+    {
+        childOut.privateKey.clear();
+        childOut.chainCode.clear();
+        errorOut = "BIP32 child derivation produced an invalid key";
+        return false;
+    }
+    return true;
+}
+
+} // namespace bitflash