(PowerShell) 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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Add-Type -Path "C:\chilkat\ChilkatDotNet47-9.5.0-x64\ChilkatDotNet47.dll"

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

$crypt = New-Object Chilkat.Crypt2

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

# This is the 2nd test vector..
$mnemonic = "legal winner thank year wave sausage worth useful legal winner thank yellow"
$passphrase = "TREZOR"
$expectedSeed = "2e8905819b8723fe2c1d161860e5ee1830318dbf49a83bd451cfb8440c28bd6fa457fe1296106559a3c80937a1c1069be3a3a5bd381ee6260e8d9739fce1f607"
$expectedMasterKey = "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.
$bdSalt = New-Object Chilkat.BinData
$bdSalt.AppendString("mnemonic","utf-8")
$bdSalt.AppendString($passphrase,"utf-8")

$computedSeed = $crypt.Pbkdf2($mnemonic,"utf-8","sha512",$bdSalt.GetEncoded("hex_lower"),2048,512,"hex_lower")

$("Expected: " + $expectedSeed)
$("Computed: " + $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
$bdSeed = New-Object Chilkat.BinData
$bdSeed.AppendEncoded($computedSeed,"hex_lower")
$crypt.EncodingMode = "hex_lower"
$crypt.HashAlgorithm = "sha512"
$crypt.SetMacKeyString("Bitcoin seed")
$hmacSha512_hex = $crypt.MacBdENC($bdSeed)

$bdHmac = New-Object Chilkat.BinData
$bdHmac.AppendEncoded($hmacSha512_hex,"hex_lower")

$bdXprv = New-Object Chilkat.BinData
$bdXprv.AppendEncoded("0488ade4","hex_lower")
$bdXprv.AppendEncoded("000000000000000000","hex_lower")
$bdXprv.AppendEncoded($bdHmac.GetEncodedChunk(32,32,"hex_lower"),"hex_lower")
$bdXprv.AppendByte(0)
$bdXprv.AppendEncoded($bdHmac.GetEncodedChunk(0,32,"hex_lower"),"hex_lower")

# Double hash using SHA256
$crypt.EncodingMode = "hex_lower"
$crypt.HashAlgorithm = "sha256"

$bdHash = New-Object Chilkat.BinData
$bdHash.AppendEncoded($crypt.HashBdENC($bdXprv),"hex_lower")
$secondHash = $crypt.HashBdENC($bdHash)
$bdHash.Clear()
$bdHash.AppendEncoded($secondHash,"hex_lower")

# Append the 1st 4 bytes of the bdHash to bdXprv.
$bdXprv.AppendEncoded($bdHash.GetEncodedChunk(0,4,"hex_lower"),"hex_lower")

# Base58 encode bdXprv
$computedMasterKey = $bdXprv.GetEncoded("base58")

$("Expected Master Key: " + $expectedMasterKey)
$("Computed Master Key: " + $computedMasterKey)