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Insecure encryption algorithm - ECB

Need​

Implementation of secure encryption algorithms

Context​

  • Usage of Java 8 for developing applications with enhanced features and performance improvements.
  • Usage of javax.crypto.Cipher for encryption and decryption operations
  • Usage of javax.crypto.spec.SecretKeySpec for generating secret keys in cryptography

Description​

Non compliant code​

import javax.crypto.Cipher;
import javax.crypto.spec.SecretKeySpec;

public class InsecureEncryption {
    public static void main(String[] args) throws Exception {
        String plainText = "This is a test.";
        String key = "1234567812345678";

        SecretKeySpec secretKeySpec = new SecretKeySpec(key.getBytes(), "AES");

        Cipher cipher = Cipher.getInstance("AES/ECB/PKCS5Padding");
        cipher.init(Cipher.ENCRYPT_MODE, secretKeySpec);

        byte[] encryptedText = cipher.doFinal(plainText.getBytes());

        System.out.println("Encrypted Text: " + new String(encryptedText));
    }
}

The above code snippet shows an example of an insecure encryption algorithm being used in a Java backend application using javax.servlet. The vulnerability lies in the usage of ECB (Electronic Codebook) mode for AES encryption.

In the code, a Cipher instance is created with the transformation string "AES/ECB/PKCS5Padding". This string specifies that the AES encryption algorithm should be used in ECB mode with PKCS5 padding.

The problem with ECB mode is that it encrypts identical plaintext blocks into identical ciphertext blocks. This means that patterns in the plaintext are preserved in the ciphertext, making the encryption susceptible to various attacks.

In particular, if an attacker has access to both the plaintext and the corresponding ciphertext, they can build a codebook of plaintext-ciphertext pairs. This codebook can then be used to decrypt other ciphertexts encrypted with the same key, effectively breaking the encryption.

This vulnerability can have serious implications for the security of the application, as it can lead to the exposure of sensitive information.

Steps​

  • Replace the insecure encryption algorithm ECB with a more secure algorithm like CBC or GCM.
  • Ensure that the encryption algorithm provides confidentiality, integrity, and authenticity.
  • Use a secure key generation mechanism to generate the encryption key.
  • Implement proper key management practices, such as securely storing and rotating encryption keys.
  • Consider using a secure random number generator for generating initialization vectors (IVs) for block cipher modes like CBC.
  • Implement proper padding schemes to prevent padding oracle attacks.
  • Regularly update and patch the encryption library to ensure that any known vulnerabilities are addressed.

Compliant code​

import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import java.security.SecureRandom;

public class SecureEncryption {
    public static void main(String[] args) throws Exception {
        String plainText = "This is a test.";
        String key = "1234567812345678";

        SecretKeySpec secretKeySpec = new SecretKeySpec(key.getBytes(), "AES");

        Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
        SecureRandom secureRandom = new SecureRandom();
        byte[] iv = new byte[cipher.getBlockSize()];
        secureRandom.nextBytes(iv);
        IvParameterSpec ivParameterSpec = new IvParameterSpec(iv);

        cipher.init(Cipher.ENCRYPT_MODE, secretKeySpec, ivParameterSpec);

        byte[] encryptedText = cipher.doFinal(plainText.getBytes());

        System.out.println("Encrypted Text: " + new String(encryptedText));
    }
}

The above code fixes the vulnerability by replacing the insecure ECB mode with the more secure CBC mode.

The Cipher.getInstance("AES/CBC/PKCS5Padding") line specifies that we are using the AES encryption algorithm in CBC mode with PKCS5 padding.

A SecureRandom object is created to generate a secure random Initialization Vector (IV). The IV is used to ensure that encrypting the same data with the same key produces different ciphertexts.

The cipher.init(Cipher.ENCRYPT_MODE, secretKeySpec, ivParameterSpec) line initializes the cipher for encryption mode with the secret key and the IV.

The cipher.doFinal(plainText.getBytes()) line encrypts the plaintext.

This code ensures that the encryption provides confidentiality, integrity, and authenticity. However, it is important to note that the key used here is a hardcoded string, which is not a secure practice. In a real-world application, you should use a secure key generation mechanism and implement proper key management practices.

References​

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