(PowerShell) Validate a JWS Using ECDSA P-521 SHA-512

Validates a JSON Web Signature (JWS) that uses ECDSA P-521 SHA-512

Note: This example requires Chilkat v9.5.0.66 or greater.

Chilkat .NET Downloads Chilkat .NET Assemblies

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

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

# Note: This example requires Chilkat v9.5.0.66 or greater.

# This example takes a JSON signature in compact serialization format,
# and uses an ECDSA public key to validate and recover the protected header and payload.

# We only need a public key for signature validation.  This is the ECDSA public key
# that is used:

#      {"kty":"EC", 
#       "crv":"P-521", 
#       "x":"AekpBQ8ST8a8VcfVOTNl353vSrDCLLJXmPk06wTjxrrjcBpXp5EOnYG_NjFZ6OvLFV1jSfS9tsz4qUxcWceqwQGk", 
#       "y":"ADSmRA43Z1DSNx_RvcLI87cdL07l6jQyyBXMoxVg_l2Th-x3S1WDhjDly79ajL4Kkd0AZMaZmh9ubmf63e3kyMj2" 
#      } 

$sbPubKey = New-Object Chilkat.StringBuilder
$sbPubKey.Append("{`"kty`":`"EC`",")
$sbPubKey.Append("`"crv`":`"P-521`",")
$sbPubKey.Append("`"x`":`"AekpBQ8ST8a8VcfVOTNl353vSrDCLLJXmPk06wTjxrrjcBpXp5EOnYG_NjFZ6OvLFV1jSfS9tsz4qUxcWceqwQGk`",")
$sbPubKey.Append("`"y`":`"ADSmRA43Z1DSNx_RvcLI87cdL07l6jQyyBXMoxVg_l2Th-x3S1WDhjDly79ajL4Kkd0AZMaZmh9ubmf63e3kyMj2`"")
$sbPubKey.Append("}")

$pubKey = New-Object Chilkat.PublicKey
$success = $pubKey.LoadFromString($sbPubKey.GetAsString())
if ($success -ne $true) {
    $($pubKey.LastErrorText)
    exit
}

$jws = New-Object Chilkat.Jws

# Set the ECC public key:
$signatureIndex = 0
$jws.SetPublicKey($signatureIndex,$pubKey)

# Load the JWS.
$sbJws = New-Object Chilkat.StringBuilder
$sbJws.Append("eyJhbGciOiJFUzUxMiJ9")
$sbJws.Append(".")
$sbJws.Append("UGF5bG9hZA")
$sbJws.Append(".")
$sbJws.Append("AdwMgeerwtHoh-l192l60hp9wAHZFVJbLfD_UxMi70cwnZOYaRI1bKPWROc-mZZq")
$sbJws.Append("wqT2SI-KGDKB34XO0aw_7XdtAG8GaSwFKdCAPZgoXD2YBJZCPEX3xKpRwcdOO8Kp")
$sbJws.Append("EHwJjyqOgzDO7iKvU8vcnwNrmxYbSW9ERBXukOXolLzeO_Jn")

$success = $jws.LoadJwsSb($sbJws)
if ($success -ne $true) {
    $($jws.LastErrorText)
    exit
}

# Validate the 1st (and only) signature at index 0..
$v = $jws.Validate($signatureIndex)
if ($v -lt 0) {
    # Perhaps Chilkat was not unlocked or the trial expired..
    $("Method call failed for some other reason.")
    $($jws.LastErrorText)
    exit
}

if ($v -eq 0) {
    $("Invalid signature.  The ECC key was incorrect, the JWS was invalid, or both.")
    exit
}

# If we get here, the signature was validated..
$("Signature validated.")
$("--")

# Recover the original content:
$("Recovered content:")
$($jws.GetPayload("utf-8"))
$("--")

# Examine the protected header:
$joseHeader = $jws.GetProtectedHeader($signatureIndex)
if ($jws.LastMethodSuccess -ne $true) {
    $("No protected header found at the given index.")
    exit
}

$joseHeader.EmitCompact = $false

$("Protected (JOSE) header:")
$($joseHeader.Emit())

# Output:
# (the string "Payload" was the content that was signed.)

# 	Signature validated.
# 	--
# 	Recovered content:
# 	Payload
# 	--
# 	Protected (JOSE) header:
# 	{
# 	  "alg": "ES512"
# 	}