(Swift 2) Create a JWS Using ECDSA P-521 SHA-512

Creates and verifies a JSON Web Signature (JWS) that uses ECDSA P-521 SHA-512

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

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func chilkatTest() {
    // 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.
    let sbJwk = CkoStringBuilder()
    sbJwk.Append("{\"kty\":\"EC\",")
    sbJwk.Append("\"crv\":\"P-521\",")
    sbJwk.Append("\"x\":\"AekpBQ8ST8a8VcfVOTNl353vSrDCLLJXmPk06wTjxrrjcBpXp5EOnYG_NjFZ6OvLFV1jSfS9tsz4qUxcWceqwQGk\",")
    sbJwk.Append("\"y\":\"ADSmRA43Z1DSNx_RvcLI87cdL07l6jQyyBXMoxVg_l2Th-x3S1WDhjDly79ajL4Kkd0AZMaZmh9ubmf63e3kyMj2\",")
    sbJwk.Append("\"d\":\"AY5pb7A0UFiB3RELSD64fTLOSV_jazdF7fLYyuTw8lOfRhWg6Y6rUrPAxerEzgdRhajnu0ferB0d53vM9mE15j2C\"")
    sbJwk.Append("}")

    let eccKey = CkoPrivateKey()
    // 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..)
    var success: Bool = eccKey.LoadJwk(sbJwk.GetAsString())
    if success != true {
        print("\(eccKey.LastErrorText)")
        return
    }

    // Create the JWS Protected Header
    let jwsProtHdr = CkoJsonObject()
    jwsProtHdr.AppendString("alg", value: "ES512")

    let jws = CkoJws()

    // Set the protected header:
    var signatureIndex: Int = 0
    jws.SetProtectedHeader(signatureIndex, json: jwsProtHdr)

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

    // Set the payload.
    var bIncludeBom: Bool = false
    var payloadStr: String? = "In our village, folks say God crumbles up the old moon into stars."
    jws.SetPayload(payloadStr, charset: "utf-8", includeBom: bIncludeBom)

    // Create the JWS
    // By default, the compact serialization is used.
    var jwsCompact: String? = jws.CreateJws()
    if jws.LastMethodSuccess != true {
        print("\(jws.LastErrorText)")
        return
    }

    print("JWS: \(jwsCompact!)")

    // Note: ECC signatures use random values, so the output will be different each time a signature is produced.
    // sample output:
    // JWS: eyJhbGciOiJFUzUxMiJ9.SW4gb3VyIHZpbGxhZ2UsIGZvbGtzIHNheSBHb2QgY3J1bWJsZXMgdXAgdGhlIG9sZCBtb29uIGludG8gc3RhcnMu.AFOnOtZ8UTp-ed1PfLfXxwGU7zT_jnmGGxew-d1CP6SfKa5RUhav5mF4szhSof22JaoQ742VIa0eZ0s1rhBnj8y6APr6g6vKzIpYZlJsnjzjUwAjDQOLmcsjxrrRfATh-NEv7G0Z9FrjdJasS44tCG2EnG6aT2TW-sPG0dy5o9jUWCzi

    // Now load the JWS, validate, and recover the original text.
    let jws2 = CkoJws()

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

    var eccPubKey: CkoPublicKey? = eccKey.GetPublicKey()

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

    // Validate the 1st (and only) signature at index 0..
    var v: Int = jws2.Validate(signatureIndex).intValue
    if v < 0 {
        // Perhaps Chilkat was not unlocked or the trial expired..
        print("Method call failed for some other reason.")
        print("\(jws2.LastErrorText)")
        return
    }

    if v == 0 {
        print("Invalid signature.  The ECC key was incorrect, the JWS was invalid, or both.")
        return
    }

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

    // Recover the original content:
    print("\(jws2.GetPayload("utf-8"))")

    // Examine the protected header:
    var joseHeader: CkoJsonObject? = jws2.GetProtectedHeader(signatureIndex)
    if jws2.LastMethodSuccess != true {
        print("No protected header found at the given index.")
        return
    }

    joseHeader.EmitCompact = false

    print("Protected (JOSE) header:")
    print("\(joseHeader!.Emit())")
    joseHeader = nil

    // Output:
    // 	Signature validated.
    // 	In our village, folks say God crumbles up the old moon into stars.
    // 	Protected (JOSE) header:
    // 	{
    // 	  "alg": "ES512"
    // 	}

}