(Swift 3,4,5...) RSA Signature/Verify with .key and .cer

See more RSA Examples

Demonstrates how to use a .key file (private key) and digital certificate (.cer, public key) to create and verify an RSA signature.

Chilkat Downloads for the Swift Programming Language MAC OS X (Cocoa) Objective-C/Swift Libs iOS Objective-C/Swift Libs

func chilkatTest() {
    // 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 .key file:
    var success: Bool = privKey.loadPemFile("privateKey.key")
    if success != true {
        print("\(privKey.lastErrorText!)")
        return
    }

    var privKeyXml: String?
    // Get the private key in XML format:
    privKeyXml = privKey.getXml()

    let rsa = CkoRsa()!

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

    // Create the signature as a hex string:
    rsa.encodingMode = "hex"

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

    // Sign the string using the sha-1 hash algorithm.
    // Other valid choices are "md2", "sha256", "sha384",
    // "sha512", and "md5".
    var hexSig: String? = rsa.signStringENC(strData, hashAlg: "sha-1")

    print("\(hexSig!)")

    // Load a digital certificate from a .cer file:
    let cert = CkoCert()!

    success = cert.load(fromFile: "myCert.cer")
    if success != true {
        print("\(cert.lastErrorText!)")
        return
    }

    var pubKey: CkoPublicKey?

    pubKey = cert.exportPublicKey()

    // Now verify using a separate instance of the RSA object:
    let rsa2 = CkoRsa()!

    // Import the public key into the RSA object:
    success = rsa2.importPublicKey(pubKey!.getXml())
    if success != true {
        print("\(rsa2.lastErrorText!)")
        return
    }

    pubKey = nil

    // The signature is a hex string, so make sure the EncodingMode is correct:
    rsa2.encodingMode = "hex"

    // Verify the signature:
    success = rsa2.verifyStringENC(strData, hashAlg: "sha-1", sig: hexSig)
    if success != true {
        print("\(rsa2.lastErrorText!)")
        return
    }

    print("Success.")

}