(Visual FoxPro) 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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LOCAL loCrypt
LOCAL lcMnemonic
LOCAL lcPassphrase
LOCAL lcExpectedSeed
LOCAL lcExpectedMasterKey
LOCAL loBdSalt
LOCAL lcComputedSeed
LOCAL loBdSeed
LOCAL lcHmacSha512_hex
LOCAL loBdHmac
LOCAL loBdXprv
LOCAL loBdHash
LOCAL lcSecondHash
LOCAL lcComputedMasterKey

* This example assumes the Chilkat API to have been previously unlocked.
* See Global Unlock Sample for sample code.

* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.Crypt2')
loCrypt = CreateObject('Chilkat.Crypt2')

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

* This is the 2nd test vector..
lcMnemonic = "legal winner thank year wave sausage worth useful legal winner thank yellow"
lcPassphrase = "TREZOR"
lcExpectedSeed = "2e8905819b8723fe2c1d161860e5ee1830318dbf49a83bd451cfb8440c28bd6fa457fe1296106559a3c80937a1c1069be3a3a5bd381ee6260e8d9739fce1f607"
lcExpectedMasterKey = "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.
* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.BinData')
loBdSalt = CreateObject('Chilkat.BinData')
loBdSalt.AppendString("mnemonic","utf-8")
loBdSalt.AppendString(lcPassphrase,"utf-8")

lcComputedSeed = loCrypt.Pbkdf2(lcMnemonic,"utf-8","sha512",loBdSalt.GetEncoded("hex_lower"),2048,512,"hex_lower")

? "Expected: " + lcExpectedSeed
? "Computed: " + lcComputedSeed

* 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
* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.BinData')
loBdSeed = CreateObject('Chilkat.BinData')
loBdSeed.AppendEncoded(lcComputedSeed,"hex_lower")
loCrypt.EncodingMode = "hex_lower"
loCrypt.HashAlgorithm = "sha512"
loCrypt.SetMacKeyString("Bitcoin seed")
lcHmacSha512_hex = loCrypt.MacBdENC(loBdSeed)

* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.BinData')
loBdHmac = CreateObject('Chilkat.BinData')
loBdHmac.AppendEncoded(lcHmacSha512_hex,"hex_lower")

* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.BinData')
loBdXprv = CreateObject('Chilkat.BinData')
loBdXprv.AppendEncoded("0488ade4","hex_lower")
loBdXprv.AppendEncoded("000000000000000000","hex_lower")
loBdXprv.AppendEncoded(loBdHmac.GetEncodedChunk(32,32,"hex_lower"),"hex_lower")
loBdXprv.AppendByte(0)
loBdXprv.AppendEncoded(loBdHmac.GetEncodedChunk(0,32,"hex_lower"),"hex_lower")

* Double hash using SHA256
loCrypt.EncodingMode = "hex_lower"
loCrypt.HashAlgorithm = "sha256"

* For versions of Chilkat < 10.0.0, use CreateObject('Chilkat_9_5_0.BinData')
loBdHash = CreateObject('Chilkat.BinData')
loBdHash.AppendEncoded(loCrypt.HashBdENC(loBdXprv),"hex_lower")
lcSecondHash = loCrypt.HashBdENC(loBdHash)
loBdHash.Clear()
loBdHash.AppendEncoded(lcSecondHash,"hex_lower")

* Append the 1st 4 bytes of the bdHash to bdXprv.
loBdXprv.AppendEncoded(loBdHash.GetEncodedChunk(0,4,"hex_lower"),"hex_lower")

* Base58 encode bdXprv
lcComputedMasterKey = loBdXprv.GetEncoded("base58")

? "Expected Master Key: " + lcExpectedMasterKey
? "Computed Master Key: " + lcComputedMasterKey

RELEASE loCrypt
RELEASE loBdSalt
RELEASE loBdSeed
RELEASE loBdHmac
RELEASE loBdXprv
RELEASE loBdHash