Encryption operation mode and the padding scheme should be chosen appropriately to guarantee data confidentiality, integrity and authenticity:
- For block cipher encryption algorithms (like AES):
- The GCM (Galois Counter Mode) mode which works
internally with zero/no padding scheme, is recommended, as it is designed to provide both data authenticity (integrity) and confidentiality.
Other similar modes are CCM, CWC, EAX, IAPM and OCB.
- The CBC (Cipher Block Chaining) mode by itself provides only data confidentiality, it’s recommended to use it along with Message
Authentication Code or similar to achieve data authenticity (integrity) too and thus to prevent padding oracle attacks.
- The ECB (Electronic Codebook) mode doesn’t provide serious message confidentiality: under a given key any given plaintext block always gets
encrypted to the same ciphertext block. This mode should not be used.
- For RSA encryption algorithm, the recommended padding scheme is OAEP.
Noncompliant Code Example
val c1 = Cipher.getInstance("AES") // Noncompliant: by default ECB mode is chosen
val c2 = Cipher.getInstance("AES/ECB/NoPadding") // Noncompliant: ECB doesn't provide serious message confidentiality
val c3 = Cipher.getInstance("RSA/None/NoPadding") // Noncompliant: RSA without OAEP padding scheme is not recommanded
// Recommended for block ciphers
val c1 = Cipher.getInstance("AES/GCM/NoPadding"); // Compliant
// Recommended for RSA
val c3 = Cipher.getInstance("RSA/None/OAEPWITHSHA-256ANDMGF1PADDING") // Compliant
// or the ECB mode can be used for RSA when "None" is not available with the security provider used - in that case, ECB will be treated as "None" for RSA.
val c3 = Cipher.getInstance("RSA/ECB/OAEPWITHSHA-256ANDMGF1PADDING"); // Compliant