Insecure encryption algorithm - TripleDES - PHP

Insecure encryption algorithm - TripleDES - PHP

Need

Secure encryption algorithm for data protection

Context

  • Usage of PHP 7.1 for server-side scripting and web development
  • Usage of OpenSSL for cryptographic functions and secure communication

Description

Non compliant code

This PHP script uses the openssl_encrypt function from the OpenSSL library to encrypt some 'important data'. The encryption method used here is 'des-ecb' (Data Encryption Standard
- Electronic Codebook).

The key used for encryption is '1234567890abcdef'. The key is usually a secret key, known only to the parties who are legitimately communicating.

The in_array function checks if the cipher method ('des-ecb' in this case) is available in the openssl_get_cipher_methods() array, which contains all available cipher methods. If it is available, it proceeds to encrypt the data.

The openssl_encrypt function encrypts the data using the specified cipher method and key. The OPENSSL_RAW_DATA option tells the function to return the raw output from the encryption process.

The problem with this code is that it uses the DES (Data Encryption Standard) encryption method, which is considered weak and insecure, and it is vulnerable to various types of attacks. Furthermore, it uses the ECB (Electronic Codebook) mode, which is also considered insecure because it does not provide serious message confidentiality.

The same plaintext block will always produce the same ciphertext block, which makes it easy for an attacker to decipher the encrypted data. This is why it's recommended to use a more secure encryption method and mode, such as AES (Advanced Encryption Standard) and CBC (Cipher Block Chaining) mode.

Steps

  • Replace the DES encryption algorithm with a more secure one such as AES-256.
  • Avoid using ECB mode as it is insecure. Instead, use a mode that provides confidentiality like CBC or GCM.
  • Ensure that the encryption key is securely generated and stored. Do not hardcode the key in the code.
  • Use a secure method to generate Initialization Vector (IV) for modes like CBC or GCM.
  • Ensure that the new encryption method is included in the list of supported cipher methods.

Compliant code

The updated code now uses the AES-256 encryption algorithm in CBC mode, which is more secure than the previously used DES algorithm in ECB mode.

The encryption key is now generated using the openssl_random_pseudo_bytes function, which generates a pseudo-random string of bytes. This is more secure than hardcoding the key in the code, as it was done previously. The key length is set to 32 bytes, which is the maximum key length for AES-256.

The Initialization Vector (IV) is also generated using the openssl_random_pseudo_bytes function. The length of the IV is determined by the openssl_cipher_iv_length function, which returns the cipher method's IV length. The IV is used in CBC mode to ensure that even if the same data is encrypted twice with the same key, the output will be different.

The encrypted data is then encoded with Base64 before being outputted. This is done because the raw encrypted data may contain special characters that could cause problems when trying to display or store the data.

Finally, the code checks if the chosen cipher method is available by using the in_array function to check if the cipher method is in the array returned by openssl_get_cipher_methods. This is a good practice to ensure that the chosen cipher method is supported.

References