(Unicode C++) BIP39 Compute Binary Seed from Mnemonic

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Creates a binary seed from a mnemonic. Uses the PBKDF2 function with a mnemonic sentence (in UTF-8 NFKD) used as the password and the string "mnemonic" + passphrase (again in UTF-8 NFKD) used as the salt. The iteration count is set to 2048 and HMAC-SHA512 is used as the pseudo-random function. The length of the derived key is 512 bits (= 64 bytes).

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#include <CkCrypt2W.h>
#include <CkBinDataW.h>

void ChilkatSample(void)
    {
    // This example assumes the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    CkCrypt2W crypt;

    // Test with the test vectors at https://github.com/trezor/python-mnemonic/blob/master/vectors.json

    // This is the 2nd test vector..
    const wchar_t *mnemonic = L"legal winner thank year wave sausage worth useful legal winner thank yellow";
    const wchar_t *passphrase = L"TREZOR";
    const wchar_t *expectedSeed = L"2e8905819b8723fe2c1d161860e5ee1830318dbf49a83bd451cfb8440c28bd6fa457fe1296106559a3c80937a1c1069be3a3a5bd381ee6260e8d9739fce1f607";
    const wchar_t *expectedMasterKey = L"xprv9s21ZrQH143K2gA81bYFHqU68xz1cX2APaSq5tt6MFSLeXnCKV1RVUJt9FWNTbrrryem4ZckN8k4Ls1H6nwdvDTvnV7zEXs2HgPezuVccsq";

    // The mnemonic sentence (in UTF-8 NFKD) used as the password.
    // The string "mnemonic" + passphrase (again in UTF-8 NFKD) used as the salt.
    // The iteration count is set to 2048 and HMAC-SHA512 is used as the pseudo-random function.
    // The length of the derived key is 512 bits (= 64 bytes). 

    // We want the computed seed to be lowercase hex, therefore our salt must also be hex.
    // The seed is the keyword "mnemonic" + passphrase (in this case is "TREZOR") converted to hex.
    CkBinDataW bdSalt;
    bdSalt.AppendString(L"mnemonic",L"utf-8");
    bdSalt.AppendString(passphrase,L"utf-8");

    const wchar_t *computedSeed = crypt.pbkdf2(mnemonic,L"utf-8",L"sha512",bdSalt.getEncoded(L"hex_lower"),2048,512,L"hex_lower");

    wprintf(L"Expected: %s\n",expectedSeed);
    wprintf(L"Computed: %s\n",computedSeed);

    // To compute the hd_master_key, duplicate this Python code:

    //     def to_hd_master_key(seed: bytes, testnet: bool = False) -> str:
    //         if len(seed) != 64:
    //             raise ValueError("Provided seed should have length of 64")
    // 
    //         # Compute HMAC-SHA512 of seed
    //         seed = hmac.new(b"Bitcoin seed", seed, digestmod=hashlib.sha512).digest()
    // 
    //         # Serialization format can be found at: https://github.com/bitcoin/bips/blob/master/bip-0032.mediawiki#Serialization_format
    //         xprv = b"\x04\x88\xad\xe4"  # Version for private mainnet
    //         if testnet:
    //             xprv = b"\x04\x35\x83\x94"  # Version for private testnet
    //         xprv += b"\x00" * 9  # Depth, parent fingerprint, and child number
    //         xprv += seed[32:]  # Chain code
    //         xprv += b"\x00" + seed[:32]  # Master key
    // 
    //         # Double hash using SHA256
    //         hashed_xprv = hashlib.sha256(xprv).digest()
    //         hashed_xprv = hashlib.sha256(hashed_xprv).digest()
    // 
    //         # Append 4 bytes of checksum
    //         xprv += hashed_xprv[:4]
    // 
    //         # Return base58
    //         return b58encode(xprv)

    // First compute the HMAC-SHA512 of the computedSeed
    CkBinDataW bdSeed;
    bdSeed.AppendEncoded(computedSeed,L"hex_lower");
    crypt.put_EncodingMode(L"hex_lower");
    crypt.put_HashAlgorithm(L"sha512");
    crypt.SetMacKeyString(L"Bitcoin seed");
    const wchar_t *hmacSha512_hex = crypt.macBdENC(bdSeed);

    CkBinDataW bdHmac;
    bdHmac.AppendEncoded(hmacSha512_hex,L"hex_lower");

    CkBinDataW bdXprv;
    bdXprv.AppendEncoded(L"0488ade4",L"hex_lower");
    bdXprv.AppendEncoded(L"000000000000000000",L"hex_lower");
    bdXprv.AppendEncoded(bdHmac.getEncodedChunk(32,32,L"hex_lower"),L"hex_lower");
    bdXprv.AppendByte(0);
    bdXprv.AppendEncoded(bdHmac.getEncodedChunk(0,32,L"hex_lower"),L"hex_lower");

    // Double hash using SHA256
    crypt.put_EncodingMode(L"hex_lower");
    crypt.put_HashAlgorithm(L"sha256");

    CkBinDataW bdHash;
    bdHash.AppendEncoded(crypt.hashBdENC(bdXprv),L"hex_lower");
    const wchar_t *secondHash = crypt.hashBdENC(bdHash);
    bdHash.Clear();
    bdHash.AppendEncoded(secondHash,L"hex_lower");

    // Append the 1st 4 bytes of the bdHash to bdXprv.
    bdXprv.AppendEncoded(bdHash.getEncodedChunk(0,4,L"hex_lower"),L"hex_lower");

    // Base58 encode bdXprv
    const wchar_t *computedMasterKey = bdXprv.getEncoded(L"base58");

    wprintf(L"Expected Master Key: %s\n",expectedMasterKey);
    wprintf(L"Computed Master Key: %s\n",computedMasterKey);
    }