(Swift) RSA Sign with PKCS8 Encrypted Key

Demonstrates how to load a private key from an encrypted PKCS8 file and create an RSA digital signature (and then verify it).

Note: This example requires Chilkat v11.0.0 or greater.

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func chilkatTest() {
    var success: Bool = false

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

    let privKey = CkoPrivateKey()!

    // Load the private key from an RSA PEM file:
    success = privKey.loadAnyFormatFile("raul_privateKey.key", password: "a0123456789")
    if success == false {
        print("\(privKey.lastErrorText!)")
        return
    }

    let rsa = CkoRsa()!

    // Import the private key into the RSA component:
    success = rsa.use(privKey)
    if success == false {
        print("\(rsa.lastErrorText!)")
        return
    }

    // This example will sign a string, and receive the signature
    // in a hex-encoded string.  Therefore, set the encoding mode
    // to "hex":
    rsa.encodingMode = "hex"

    var strData: String? = "This is the string to be signed."

    // Sign the string using the sha256 hash algorithm.
    // Other valid choices are sha1, sha384, sha512 and others.
    var hexSig: String? = rsa.signStringENC(strData, hashAlg: "sha256")
    if rsa.lastMethodSuccess == false {
        print("\(rsa.lastErrorText!)")
        return
    }

    print("\(hexSig!)")

    // Now verify with the public key.
    // This example shows how to use the public key from 
    // a digital certificate (.cer file)
    let cert = CkoCert()!
    success = cert.load(fromFile: "raul_publicKey.cer")
    if success == false {
        print("\(cert.lastErrorText!)")
        return
    }

    let pubKey = CkoPublicKey()!
    cert.get(pubKey)

    let rsa2 = CkoRsa()!
    success = rsa2.use(pubKey)
    if success == false {
        print("\(rsa2.lastErrorText!)")
        return
    }

    // Verify the signature against the original data:
    rsa2.encodingMode = "hex"
    success = rsa2.verifyStringENC(strData, hashAlg: "sha256", sig: hexSig)
    if success == false {
        print("\(rsa2.lastErrorText!)")
        return
    }

    print("Signature verified!")

    // Verify with incorrect data:
    success = rsa2.verifyStringENC("something else", hashAlg: "sha256", sig: hexSig)
    if success != true {
        print("Signature not verified! (which was expected in this case)")
    }
    else {
        print("Hmmm... that's not right...")
    }


}