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Use of a broken or weak cryptographic algorithm

ID: py/weak-cryptographic-algorithm Kind: problem Security severity: 7.5 Severity: warning Precision: high Tags: - security - external/cwe/cwe-327 Query suites: - python-code-scanning.qls - python-security-extended.qls - python-security-and-quality.qls

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Using broken or weak cryptographic algorithms may compromise security guarantees such as confidentiality, integrity, and authenticity.

Many cryptographic algorithms are known to be weak or flawed. The security guarantees of a system often rely on the underlying cryptography, so using a weak algorithm can have severe consequences. For example:

  • If a weak encryption algorithm is used, an attacker may be able to decrypt sensitive data.

  • If a weak algorithm is used for digital signatures, an attacker may be able to forge signatures and impersonate legitimate users. This query alerts on any use of a weak cryptographic algorithm that is not a hashing algorithm. Use of broken or weak cryptographic hash functions are handled by the py/weak-sensitive-data-hashing query.

Recommendation

Ensure that you use a strong, modern cryptographic algorithm, such as AES-128 or RSA-2048.

Example

The following code uses the pycryptodome library to encrypt some secret data. When you create a cipher using pycryptodome you must specify the encryption algorithm to use. The first example uses DES, which is an older algorithm that is now considered weak. The second example uses AES, which is a stronger modern algorithm.

from Crypto.Cipher import DES, AES cipher = DES.new(SECRET_KEY) def send_encrypted(channel, message): channel.send(cipher.encrypt(message)) # BAD: weak encryption cipher = AES.new(SECRET_KEY) def send_encrypted(channel, message): channel.send(cipher.encrypt(message)) # GOOD: strong encryption

NOTICE: the original [pycrypto](https://pypi.org/project/pycrypto/) PyPI package that provided the Crypto module is not longer actively maintained, so you should use the [pycryptodome](https://pypi.org/project/pycryptodome/) PyPI package instead (which has a compatible API).

References