(PowerShell) ECDSA Sign Data and Get Raw R and S Values

Demonstrates getting the raw R and S value of an ECDSA signature.

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

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

# To create an ECDSA signature, the data first needs to be hashed.  Then the hash
# is signed.

$crypt = New-Object Chilkat.Crypt2
$crypt.HashAlgorithm = "SHA256"
$crypt.Charset = "utf-8"
$crypt.EncodingMode = "base64"

# Hash a string.
$hash1 = $crypt.HashStringENC("The quick brown fox jumps over the lazy dog")
$("hash1 = " + $hash1)

# -----------------------------------------------------------
# An ECDSA private key is used for signing.  The public key is for signature verification.
# Load our ECC private key.
# Our private key file contains this:

# 	// -----BEGIN PRIVATE KEY-----
# 	MIGHAgEAMBMGByqGSM49AgEGCCqGSM49AwEHBG0wawIBAQQg3J8q/24D1sEKGdP9
# 	72MGYElLGpw/a56Y3t6pfON3uhShRANCAATlSmoizyhAwoYZAOuFBATl07/1RR54
# 	a1Dzfm16grxJe666AGKR+bSs24hk7TEpaeCTvT8YOOM3l+xKFg7zq6Q9
# 	-----END PRIVATE KEY-----

$privKey = New-Object Chilkat.PrivateKey
$success = $privKey.LoadPemFile("qa_data/ecc/secp256r1-key-pkcs8.pem")
if ($success -ne $true) {
    $($privKey.LastErrorText)
    exit
}

# Sign the hash..
$prng = New-Object Chilkat.Prng
$ecdsa = New-Object Chilkat.Ecc
$ecdsaSigBase64 = $ecdsa.SignHashENC($hash1,"base64",$privKey,$prng)
if ($ecdsa.LastMethodSuccess -ne $true) {
    $($ecdsa.LastErrorText)
    exit
}

# The ECDSA signature is ASN.1 that contains a sequence of 2 large integers (r and s)
# For example:
# SEQUENCE (2 elem)
#   INTEGER (255 bit) 792134D9B4AD82D5431ED03835A88E2596EB35E5B13054BD9B05A0069281ACC9
#   INTEGER (255 bit) 481E758CC1E3CBF825537EC3D9A2CA627E5FAD1137BBEA65DF38658DCB0A9ED5

$("Base64 ECDSA signature = " + $ecdsaSigBase64)

# If the raw R and S values are needed, here's how to get them:
$asn = New-Object Chilkat.Asn
$success = $asn.LoadEncoded($ecdsaSigBase64,"base64")
if ($success -eq $false) {
    $($asn.LastErrorText)
    exit
}

# The R and X will be in hexidecimal in the XML.
$xml = New-Object Chilkat.Xml
$xml.LoadXml($asn.AsnToXml())
$($xml.GetXml())

# The XML looks like this:
# <sequence>
# <int>792134D9B4AD82D5431ED03835A88E2596EB35E5B13054BD9B05A0069281ACC9</int>
# <int>481E758CC1E3CBF825537EC3D9A2CA627E5FAD1137BBEA65DF38658DCB0A9ED5</int>
# </sequence>

# Copy raw R and S hex values into a Chilkat BinData object.
$bd = New-Object Chilkat.BinData
$r = $xml.GetChildContent("int[0]")
$s = $xml.GetChildContent("int[1]")
$bd.AppendEncoded($r,"hex")
$bd.AppendEncoded($s,"hex")

$("Number of bytes in bd: " + $bd.NumBytes)