(Swift 3,4,5...) Verify the RSA Signature of a SHA256 Hash

See more RSA Examples

Demonstrates how to verify an RSA signature of a SHA256 hash.

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's say you have a file containing the 32-bytes of a SHA256 hash,
    // and a file that is an RSA signature of those 32 bytes.
    // Here's how you verify using the RSA public key found in a PEM.

    let pubKey = CkoPublicKey()!
    var success: Bool = pubKey.load(fromFile: "rsaPubKey.pem")
    if success == false {
        print("\(pubKey.lastErrorText!)")
        return
    }

    let rsa = CkoRsa()!

    // Get the public key.
    success = rsa.importPublicKeyObj(pubKey)
    if success == false {
        print("\(rsa.lastErrorText!)")
        return
    }

    // Get the 32-byte SHA256 hash.
    let bdHash = CkoBinData()!
    success = bdHash.loadFile("myHash.sha256")
    if success == false {
        print("Failed to load SHA256 hash.")
        return
    }

    // Get the RSA signature to be validated.
    let bdSig = CkoBinData()!
    success = bdSig.loadFile("mySig.sig")
    if success == false {
        print("Failed to load RSA signature.")
        return
    }

    // Verify the signature against the SHA256 hash.
    var enc: String? = "base64"
    rsa.encodingMode = enc
    success = rsa.verifyHashENC(bdHash.getEncoded(enc), hashAlg: "sha256", encodedSig: bdSig.getEncoded(enc))
    if success == false {
        print("\(rsa.lastErrorText!)")
        return
    }

    print("Signature validated.")

}