(Swift 2) JWS Using HMAC SHA-256

Creates a JSON Web Signatures (JWS) using HMAC SHA-256.

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.

    var success: Bool

    // First create the JWS Protected Header
    let jwsProtHdr = CkoJsonObject()
    jwsProtHdr.AppendString("typ", value: "JWT")
    jwsProtHdr.AppendString("alg", value: "HS256")
    print("JWS Protected Header: \(jwsProtHdr.Emit())")

    // Output:
    // JWS Protected Header: {"typ":"JWT","alg":"HS256"}

    let jws = CkoJws()

    // Set the HMAC key:
    var hmacKey: String? = "AyM1SysPpbyDfgZld3umj1qzKObwVMkoqQ-EstJQLr_T-1qS0gZH75aKtMN3Yj0iPS4hcgUuTwjAzZr1Z9CAow"
    var signatureIndex: Int = 0
    jws.SetMacKey(signatureIndex, key: hmacKey, encoding: "base64url")

    // Set the protected header:
    jws.SetProtectedHeader(signatureIndex, json: jwsProtHdr)

    // 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!)")

    // sample output:
    // JWS: eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.SW4gb3VyIHZpbGxhZ2UsIGZvbGtzIHNheSBHb2QgY3J1bWJsZXMgdXAgdGhlIG9sZCBtb29uIGludG8gc3RhcnMu.bsYsi8HJ0N6OqGI1hKQ9QQRNPxxA5qMpcHLtOvXatk8

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

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

    // Set the MAC key used for validation.
    signatureIndex = 0
    jws2.SetMacKey(signatureIndex, key: hmacKey, encoding: "base64url")

    // 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 MAC 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:
    // 	{ 
    // 	  "typ": "JWT",
    // 	  "alg": "HS256"
    // 	} 

}