Swift

Decrypt 256-bit AES GCM Produced by Something Unknown

See more Encryption Examples

Demonstrates how to decrypt something produced elsewhere (unknown) with 256-bit AES GCM. Swift

func chilkatTest() {
    var success: Bool = false

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

    // We have the following to decrypt:

    // Key (Base64): 
    var keyBase64: String? = "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"

    // IV (Base64Url):
    var ivBase64Url: String? = "xrvaINMLqotAbWRK"

    // ciphertext (base64url):
    var cipherBase64Url: String? = "RtGNAS-zQOxSB8W0HfqJjCoyt9KgImW_l-HjVC40hOOl-RNfRF3hzDIT1kvFVF8i_KX9XmqAftb6lyq-jLCEc_MSgqt3q1ixv3Ez4SbS3G5e3qGzLwxIMi2sCt00aDNwK2ipsJ4aw8s7ePPnl4oY-y1st9rwCWR0rrgEZwS9jmS4uJWGPn9K3jbKRnMslznDbtFLNJctMVXBTP-cv47JelxLCBOQSlK29rMuEFrhHR_VQrPq6gtZaBVSXZSYT0XOklp7nu9mVhrMCRtBCC5oiu5MPE5JYx4ANo3hUY7_NyQl2bpn9GfRXrdvqRGE-gy2upj-cDkm0t_tV8xmYge9DBQTH3B_4BGl2qTk_o-m7pEmKkS8XSdQhGcuFlykqrkE8SzB5I8esfzWOM0pwxbz0H_VaylKYHY="

    let crypt = CkoCrypt2()!

    crypt.cryptAlgorithm = "aes"
    crypt.cipherMode = "gcm"
    crypt.keyLength = 256

    success = crypt.setEncodedAad(aadStr: "random", encoding: "ascii")
    crypt.setEncodedKey(keyStr: keyBase64, encoding: "base64")
    crypt.setEncodedIV(ivStr: ivBase64Url, encoding: "base64url")

    // The cipher text contains the 16-byte auth tag at the end.
    // get it separately..
    let bdEncrypted = CkoBinData()!
    let bdAuthTag = CkoBinData()!
    success = bdEncrypted.appendEncoded(encData: cipherBase64Url, encoding: "base64url")

    var numBytes: Int = bdEncrypted.numBytes.intValue
    var authTagHex: String? = bdEncrypted.getEncodedChunk(offset: numBytes - 16, numBytes: 16, encoding: "hex")

    print("Auth tag in hex: \(authTagHex!)")

    success = bdAuthTag.appendEncoded(encData: authTagHex, encoding: "hex")
    bdEncrypted.removeChunk(offset: numBytes - 16, numBytes: 16)

    // Use this special value to tell Chilkat to ignore the auth tag.
    success = crypt.setEncodedAuthTag(authTagStr: "FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF", encoding: "hex")

    // Decrypt
    crypt.encodingMode = "base64"
    var originalText: String? = crypt.decryptStringENC(str: bdEncrypted.getEncoded(encoding: "base64"))
    if crypt.lastMethodSuccess == false {
        print("\(crypt.lastErrorText!)")
    }
    else {
        print("\(originalText!)")
        print("Success.")
    }

    // Decrypted text

}