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Insecure encryption algorithm - Blowfish

Need​

Secure encryption algorithm for protecting sensitive information

Context​

  • Usage of Swift for iOS and macOS app development
  • Usage of UIKit for building modern and responsive user interfaces
  • Usage of CryptoSwift for cryptographic operations in Swift

Description​

Non compliant code​

import UIKit
import CryptoSwift

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        let originalString = "password"
        let key = "secret0key000000" // secret key
        let iv = "0123456789012345" // initialization vector

        do {
            let encrypted = try Blowfish(key: key, blockMode: CBC(iv: iv), padding: .pkcs7).encrypt(Array(originalString.utf8))
            print("Encrypted: \\(encrypted.toHexString())")
        } catch {
            print(error)
        }
    }
}

This Swift code snippet is an example of a mobile application for iOS that uses the Blowfish encryption algorithm, which is considered insecure.

The ViewController class has a viewDidLoad method where the encryption process happens. In this method, an original string "password" is defined, which is to be encrypted. A secret key "secret0key000000" and an initialization vector "iv" "0123456789012345" are also defined.

The Blowfish encryption method is then invoked with the secret key, block mode set to CBC with the initialization vector, and padding set to .pkcs7. The Array(originalString.utf8) is then encrypted, and the encrypted hexadecimal string is printed.

The vulnerability lies in the usage of the Blowfish encryption algorithm. Blowfish is an older symmetric encryption algorithm which is considered to be insecure for many applications. It has a relatively small key size, which makes it susceptible to brute force attacks. Moreover, its encryption method is not as strong as more modern algorithms. Therefore, sensitive information encrypted with Blowfish could be at risk of being decrypted and exposed.

Steps​

  • Replace the insecure encryption algorithm (Blowfish) with a more secure algorithm, such as AES (Advanced Encryption Standard).
  • Ensure that the encryption algorithm is implemented correctly and follows best practices.
  • Use a strong and unique encryption key for each encryption operation.
  • Generate a random initialization vector (IV) for each encryption operation.
  • Implement proper padding scheme, such as PKCS7, to ensure data integrity.
  • Regularly update the encryption algorithm and libraries to stay protected against new vulnerabilities and attacks.

Compliant code​

import UIKit
import CryptoSwift

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        let originalString = "password"
        let key = "secret0key000000" // secret key
        let iv = AES.randomIV(AES.blockSize) // initialization vector

        do {
            let aes = try AES(key: key.bytes, blockMode: CBC(iv: iv), padding: .pkcs7)
            let encrypted = try aes.encrypt(Array(originalString.utf8))
            print("Encrypted: \\(encrypted.toHexString())")
        } catch {
            print(error)
        }
    }
}

The above code is a fixed version of the original vulnerable code. The main change is the replacement of the insecure Blowfish encryption algorithm with the more secure AES (Advanced Encryption Standard) algorithm.

Here are the changes in detail:

  • AES encryption algorithm: AES is a secure encryption algorithm and is widely accepted as the most secure symmetric encryption algorithm available today. It is used in place of the insecure Blowfish algorithm.

  • Random Initialization Vector (IV): A new random IV is generated for each encryption operation using AES.randomIV(AES.blockSize). This is more secure than using a fixed IV, as it makes the encryption more unpredictable and harder to break.

  • PKCS7 padding: The PKCS7 padding scheme is used to ensure data integrity. This padding scheme adds extra bytes to the data to make it fit into an exact number of encryption blocks, which helps prevent data corruption and makes the encryption more secure.

  • Error handling: If an error occurs during the encryption process, it is caught and printed to the console. This allows for easier debugging and ensures that the program doesn't crash unexpectedly.

Remember to keep your encryption libraries up to date to protect against new vulnerabilities and attacks. Also, ensure that the encryption key is strong and unique for each encryption operation.

References​

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