iOS Swift 4:How to perform encryption/decryption with DES-ECB-PKCS5Padding?

Question

I want to perform encryption/decryption with DES-ECB-PKCS5Padding in iOS Swift.

I have some code from Server Side (most probably in ActionScript) to help which is as follows:

private static const type:String='simple-des-ecb';

public static function encrypt(txt:String, salt:String): String
{
    var key:ByteArray = Hex.toArray(Hex.fromString(salt));
    var data:ByteArray = Hex.toArray(Hex.fromString(txt));
    var pad:IPad = new PKCS5;
    var mode:ICipher = Crypto.getCipher(type, key, pad);
    pad.setBlockSize(mode.getBlockSize());
    mode.encrypt(data);
    data.position = 0;
    return Base64.encodeByteArray(data);
}

public static function decrypt(txt:String, salt:String): String
{
    var key:ByteArray = Hex.toArray(Hex.fromString(salt));
    var data:ByteArray = Base64.decodeToByteArray(txt);
    var pad:IPad = new PKCS5;
    var mode:ICipher = Crypto.getCipher(type, key, pad);
    pad.setBlockSize(mode.getBlockSize());
    try
    {
        mode.decrypt(data);
    }
    catch (e:Error)
    {
        trace(e.message);
        trace(e.getStackTrace());
    }
    return Hex.toString(Hex.fromArray(data));
}

I have tried to reciprocate the above functions in Swift, but I'm unable to get desired results

My Swift code goes as follows:

func encrypt(text: String, salt: String) -> String {

    let strHexKey = hexFromString(string: salt)
    let key = strHexKey.hexaBytes

    let strHexData = hexFromString(string: text)
    let data = strHexData.hexaBytes

    let cryptor = Cryptor(operation: .encrypt, algorithm: .des, options: .PKCS7Padding, key: key, iv: Array<UInt8>())
    let cipherText = cryptor.update(byteArray: data)?.final()

    let strBase64 = cipherText!.data.base64EncodedString()

    return strBase64

}

func decrypt(text: String, salt: String) -> String {

    let strHexKey = hexFromString(string: salt)
    let key = arrayFrom(hexString: strHexKey)

    let data = text.fromBase64()?.data(using: .utf8)

    let cryptor = Cryptor(operation: .decrypt, algorithm: .des, options: .PKCS7Padding, key: key, iv: Array<UInt8>())
    let cipherText = cryptor.update(data: data!)!.final()

    return (cipherText?.hexa)!

}

I have been using https://github.com/iosdevzone/IDZSwiftCommonCrypto for Cryptor Library.

Could you provide a sample input and output that generated by server-side ? — Arash Etemad, Dec 25 '18 at 11:12
@arash Text - dimusco@yopmail.com . Salt - 123456 . Output - eLnJvMUKApg= — Vaibhav Jhaveri, Dec 26 '18 at 06:00
You supply IV, however, you should use [Mode ECB](https://github.com/iosdevzone/IDZSwiftCommonCrypto/blob/master/IDZSwiftCommonCrypto/StreamCryptor.swift) — kelalaka, Dec 28 '18 at 07:06
@kelalaka How to supply IV? The ActionScript code snippet doesn't mention the use of IV — Vaibhav Jhaveri, Dec 28 '18 at 08:06
https://academy.realm.io/posts/danny-keogan-swift-cryptography/ — kelalaka, Dec 28 '18 at 10:06
@kelalaka I have used the same library, but it does not support PKCS 5 padding — Vaibhav Jhaveri, Dec 28 '18 at 12:01
I cannot talk about every lib, but see [this](https://stackoverflow.com/questions/53941878/can-i-use-pkcs5padding-padding-algorithm-while-decryption-for-already-encrypted) — kelalaka, Dec 28 '18 at 12:10

Stephan Schlecht · Answer 1 · 2019-01-02T00:39:58.677

Swift Code

A conversion of the ActionScript code to Swift could look like this:

func encrypt(text: String, salt: String) -> String? {
    let key = Array(salt.utf8)
    let bytes = Array(text.utf8)
    let cryptor = Cryptor(operation: .encrypt, algorithm: .des, options: [.ECBMode, .PKCS7Padding], key: key, iv:[UInt8]())
    if let encrypted = cryptor.update(byteArray: bytes)?.final() {
        return Data(encrypted).base64EncodedString()
    }
    return nil
}

func decrypt(text: String, salt: String) -> String? {
    let key = Array(salt.utf8)
    let bytes = [UInt8](Data(base64Encoded: text)!)
    let cryptor = Cryptor(operation: .decrypt, algorithm: .des, options: [.ECBMode, .PKCS7Padding], key: key, iv:[UInt8]())
    if let decrypted = cryptor.update(byteArray: bytes)?.final() {
        return String(bytes: decrypted, encoding: .utf8)
    }
    return nil
}

Quick Test

In the comments you used as a test case with text dimusco@yopmail.com and salt: 123456. This would be called like this:

let salt = "123456"
if let encrypted = self.encrypt(text: "dimusco@yopmail.com", salt: salt) {
    print ("encrypted: " + encrypted)
    if let decrypted = self.decrypt(text: encrypted, salt: salt) {
        print ("decrypted: " + decrypted)
    }
}

The correct output would be:

encrypted: +rptz3Ss8zh2j0VXN7CICsi2jkzYoAPx
decrypted: dimusco@yopmail.com

I don't know where you got your result eLnJvMUKApg= from, but it's wrong. Also the ActionScript code you are quoting in your question would give the result +rptz3Ss8zh2j0VXN7CICsi2jkzYoAPx.

Compare with ActionScript

Flex

You can download the free flex sdk from here:

https://download.macromedia.com/pub/flex/sdk/flex_sdk_4.6.zip

as3crypto Library

The ActionScript quoted seems to use a library called as3crypto, which can be downloaded from here:

https://code.google.com/archive/p/as3crypto/

Flex depends on an installed Java environment. It doesn't seem to work with the latest version of Java out of the box, but you can use Java 1.6 for example.

You can create a small ActionScript program that calls the as3crypto routines. If the file is called e.g. Main.as, it can be compiled with the following command:

flex_sdk_4.6/bin/mxmlc Main.as

The output is then a Main.swf file, which can be executed with the Flash plugin in a browser.

Result

The result of the ActionScript code is the same as the Swift code, see here this screenshot:

The Github link is provided by the OP at the end of the question. Had a quick look, the project is still available at that link. — Stephan Schlecht, Jul 10 '22 at 19:14

iOS Swift 4:How to perform encryption/decryption with DES-ECB-PKCS5Padding?

1 Answers1