Use of a cryptographic algorithm with insufficient key size

Modern encryption relies on the computational infeasibility of breaking a cipher and decoding its message without the key. As computational power increases, the ability to break ciphers grows, and key sizes need to become larger as a result. Cryptographic algorithms that use too small of a key size are vulnerable to brute force attacks, which can reveal sensitive data.

Recommendation

Use a key of the recommended size or larger. The key size should be at least 128 bits for AES encryption, 256 bits for elliptic-curve cryptography (ECC), and 2048 bits for RSA, DSA, or DH encryption.

Example

The following code uses cryptographic algorithms with insufficient key sizes.

    KeyPairGenerator keyPairGen1 = KeyPairGenerator.getInstance("RSA");
    keyPairGen1.initialize(1024); // BAD: Key size is less than 2048

    KeyPairGenerator keyPairGen2 = KeyPairGenerator.getInstance("DSA");
    keyPairGen2.initialize(1024); // BAD: Key size is less than 2048

    KeyPairGenerator keyPairGen3 = KeyPairGenerator.getInstance("DH");
    keyPairGen3.initialize(1024); // BAD: Key size is less than 2048

    KeyPairGenerator keyPairGen4 = KeyPairGenerator.getInstance("EC");
    ECGenParameterSpec ecSpec = new ECGenParameterSpec("secp112r1"); // BAD: Key size is less than 256
    keyPairGen4.initialize(ecSpec);

    KeyGenerator keyGen = KeyGenerator.getInstance("AES");
    keyGen.init(64); // BAD: Key size is less than 128

To fix the code, change the key sizes to be the recommended size or larger for each algorithm.

References

• Wikipedia: Key size.
• Wikipedia: Strong cryptography.
• OWASP: Cryptographic Storage Cheat Sheet.
• OWASP: Testing for Weak Encryption.
• NIST: Transitioning the Use of Cryptographic Algorithms and Key Lengths.
• Common Weakness Enumeration: CWE-326.