(Xojo Plugin) Create a JWS Using ECDSA P-256 SHA-256

Creates and validates a JSON Web Signature (JWS) that uses ECDSA P-256 SHA-256

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

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// 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.

// Use the following ECC key loaded from JWK format.
Dim sbJwk As New Chilkat.StringBuilder
Dim success As Boolean
success = sbJwk.Append("{""kty"":""EC"",")
success = sbJwk.Append("""crv"":""P-256"",")
success = sbJwk.Append("""x"":""f83OJ3D2xF1Bg8vub9tLe1gHMzV76e8Tus9uPHvRVEU"",")
success = sbJwk.Append("""y"":""x_FEzRu9m36HLN_tue659LNpXW6pCyStikYjKIWI5a0"",")
success = sbJwk.Append("""d"":""jpsQnnGQmL-YBIffH1136cspYG6-0iY7X1fCE9-E9LI""")
success = sbJwk.Append("}")

Dim eccKey As New Chilkat.PrivateKey
// Note: This example loads the ECDSA key from JWK format.  Any format can be loaded
// into the private key object. (See the online reference documentation..)
Dim success As Boolean
success = eccKey.LoadJwk(sbJwk.GetAsString())
If (success <> True) Then
    System.DebugLog(eccKey.LastErrorText)
    Return
End If

// Create the JWS Protected Header
Dim jwsProtHdr As New Chilkat.JsonObject
success = jwsProtHdr.AppendString("alg","ES256")

Dim jws As New Chilkat.Jws

// Set the protected header:
Dim signatureIndex As Int32
signatureIndex = 0
success = jws.SetProtectedHeader(signatureIndex,jwsProtHdr)

// Set the ECC key:
success = jws.SetPrivateKey(signatureIndex,eccKey)

// Set the payload.
Dim bIncludeBom As Boolean
bIncludeBom = False
Dim payloadStr As String
payloadStr = "In our village, folks say God crumbles up the old moon into stars."
success = jws.SetPayload(payloadStr,"utf-8",bIncludeBom)

// Create the JWS
// By default, the compact serialization is used.
Dim jwsCompact As String
jwsCompact = jws.CreateJws()
If (jws.LastMethodSuccess <> True) Then
    System.DebugLog(jws.LastErrorText)
    Return
End If

System.DebugLog("JWS: " + jwsCompact)

// Note: ECC signatures use random values, so the output will be different each time a signature is produced.
// sample output:
// JWS: eyJhbGciOiJFUzI1NiJ9.SW4gb3VyIHZpbGxhZ2UsIGZvbGtzIHNheSBHb2QgY3J1bWJsZXMgdXAgdGhlIG9sZCBtb29uIGludG8gc3RhcnMu.J6EGTNkeuEjehHHBu0SOKzifm8r35wbx49A5964pxzB7gannyZZPMkK7vmlaPJ-K8Xmm8cZsQySAPC12Xd8avw

// Now load the JWS, validate, and recover the original text.
Dim jws2 As New Chilkat.Jws

// Load the JWS.
success = jws2.LoadJws(jwsCompact)

Dim eccPubKey As Chilkat.PublicKey
eccPubKey = eccKey.GetPublicKey()

// Set the ECC public key used for validation.
signatureIndex = 0
success = jws2.SetPublicKey(signatureIndex,eccPubKey)

// Validate the 1st (and only) signature at index 0..
Dim v As Int32
v = jws2.Validate(signatureIndex)
If (v < 0) Then
    // Perhaps Chilkat was not unlocked or the trial expired..
    System.DebugLog("Method call failed for some other reason.")
    System.DebugLog(jws2.LastErrorText)
    Return
End If

If (v = 0) Then
    System.DebugLog("Invalid signature.  The ECC key was incorrect, the JWS was invalid, or both.")
    Return
End If

// If we get here, the signature was validated..
System.DebugLog("Signature validated.")

// Recover the original content:
System.DebugLog(jws2.GetPayload("utf-8"))

// Examine the protected header:
Dim joseHeader As Chilkat.JsonObject
joseHeader = jws2.GetProtectedHeader(signatureIndex)
If (jws2.LastMethodSuccess <> True) Then
    System.DebugLog("No protected header found at the given index.")
    Return
End If

joseHeader.EmitCompact = False

System.DebugLog("Protected (JOSE) header:")
System.DebugLog(joseHeader.Emit())

// Output:

// Signature validated.
// In our village, folks say God crumbles up the old moon into stars.
// Protected (JOSE) header:
// { 
//   "alg": "ES256"
// }