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Insecure encryption algorithm - Cipher Block Chaining

Need​

Implementation of secure encryption algorithms with strong cipher block chaining

Context​

  • Usage of Scala for building scalable and high-performance applications
  • Usage of javax.crypto for cryptographic operations in Java

Description​

Non compliant code​

import javax.crypto.Cipher
import javax.crypto.spec.SecretKeySpec
import javax.crypto.spec.IvParameterSpec

val key = "1234567812345678"
val iv = "1234567812345678"

val secretKeySpec = new SecretKeySpec(key.getBytes, "AES")
val ivParameterSpec = new IvParameterSpec(iv.getBytes)

val cipher = Cipher.getInstance("AES/CBC/PKCS5Padding")
cipher.init(Cipher.ENCRYPT_MODE, secretKeySpec, ivParameterSpec)

val plaintext = "Sensitive Information"
val cipherText = cipher.doFinal(plaintext.getBytes)

In the above code, we are using AES encryption with Cipher Block Chaining (CBC) mode. Here's a step-by-step breakdown of what the code does:

  1. We import the necessary libraries for encryption.
  2. We define a key and initialization vector (IV) as simple strings. In a real-world scenario, these should be securely generated and stored.
  3. We create a SecretKeySpec and IvParameterSpec using the key and IV.
  4. We create a Cipher instance using the AES algorithm in CBC mode with PKCS5Padding.
  5. We initialize the cipher in encryption mode using the secret key and IV.
  6. We define a plaintext string that represents the sensitive data we want to encrypt.
  7. We encrypt the plaintext using the doFinal method of the cipher, which results in the ciphertext.

The vulnerability here is that we are using CBC mode for encryption, which is susceptible to certain types of attacks, such as the bit-flipping attack. This is because CBC mode uses each ciphertext block to encrypt the next plaintext block, which means that if an attacker can guess the plaintext of one block, they can use this to decipher subsequent blocks.

Additionally, the use of a static, hard-coded key and IV in the code is a security risk. These should be securely generated and stored, and not visible in the code.

This code should be refactored to use a more secure mode of operation, such as GCM (Galois/Counter Mode), which provides both data authenticity (integrity) and confidentiality. The key and IV should also be securely generated and stored.

Steps​

  • Replace the insecure encryption algorithm with a secure one.
  • Use a strong encryption algorithm like AES-GCM or ChaCha20-Poly1305.
  • Ensure that the encryption algorithm provides both confidentiality and integrity protection.
  • Generate a secure random key and initialization vector (IV) for each encryption operation.
  • Do not hardcode the key and IV in the code.
  • Store the key and IV securely, such as in a secure key management system or environment variables.
  • Use a secure key derivation function to derive the encryption key from a password or passphrase, if applicable.
  • Ensure that the encryption operation uses authenticated encryption to prevent tampering with the ciphertext.
  • Consider using a higher-level encryption library or framework that abstracts away the low-level details of encryption.
  • Regularly update the encryption algorithm and cryptographic libraries to stay protected against new vulnerabilities and attacks.

Compliant code​

import javax.crypto.Cipher
import javax.crypto.spec.GCMParameterSpec
import javax.crypto.spec.SecretKeySpec
import java.security.SecureRandom
import java.util.Base64

val secureRandom = new SecureRandom()
val key = new Array[Byte](16)
val iv = new Array[Byte](12)

secureRandom.nextBytes(key)
secureRandom.nextBytes(iv)

val secretKeySpec = new SecretKeySpec(key, "AES")
val gcmParameterSpec = new GCMParameterSpec(128, iv)

val cipher = Cipher.getInstance("AES/GCM/NoPadding")
cipher.init(Cipher.ENCRYPT_MODE, secretKeySpec, gcmParameterSpec)

val plaintext = "Sensitive Information"
val cipherText = cipher.doFinal(plaintext.getBytes)

val encodedKey = Base64.getEncoder.encodeToString(key)
val encodedIv = Base64.getEncoder.encodeToString(iv)

println(s"Key: $encodedKey")
println(s"IV: $encodedIv")

The above code fixes the vulnerability by replacing the insecure encryption algorithm with a secure one, AES-GCM.

AES-GCM is a block cipher mode of operation that provides high speed of authenticated encryption and data integrity.

The key and initialization vector (IV) are generated securely using SecureRandom. This ensures that they are unique and unpredictable for each encryption operation.

The key and IV are then encoded to a Base64 string for safe storage and transmission. They should be stored securely, such as in a secure key management system or environment variables, and not hardcoded in the code.

The encryption operation uses authenticated encryption, which prevents tampering with the ciphertext.

The code uses the Cipher class from the Java Cryptography Extension (JCE) to perform the encryption. The Cipher instance is initialized with the encryption mode, key, and IV.

The plaintext is then encrypted using the doFinal method, which performs the encryption operation and returns the ciphertext.

The code does not use any password or passphrase to derive the encryption key. If a password or passphrase is used, a secure key derivation function should be used to derive the encryption key.

The code should be regularly updated to use the latest encryption algorithm and cryptographic libraries to stay protected against new vulnerabilities and attacks.

Consider using a higher-level encryption library or framework that abstracts away the low-level details of encryption.

References​

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