Cryptographic hash algorithms such as MD2, MD4, MD5, MD6, HAVAL-128, DSA (which uses SHA-1), RIPEMD, RIPEMD-128, RIPEMD-160and SHA-1 are no longer considered secure, because it is possible to have collisions (little computational effort is enough to find two or more different inputs that produce the same hash).

Message authentication code (MAC) algorithms such as HMAC-MD5 or HMAC-SHA1 use weak hash functions as building blocks. Although they are not all proven to be weak, they are considered legacy algorithms and should be avoided.

Ask Yourself Whether

The hashed value is used in a security context like:

There is a risk if you answered yes to any of those questions.

Recommended Secure Coding Practices

Safer alternatives, such as SHA-256, SHA-512, SHA-3 are recommended, and for password hashing, it’s even better to use algorithms that do not compute too "quickly", like bcrypt, scrypt, argon2 or pbkdf2 because it slows down brute force attacks.

Sensitive Code Example

$hash = md5($data); // Sensitive
$hash = sha1($data);   // Sensitive

Compliant Solution

// for a password
$hash = password_hash($password, PASSWORD_BCRYPT); // Compliant

// other context
$hash = hash("sha512", $data);

See