Security: Encryption, Hashing and PHP

Security: Encryption, Hashing and PHP Show Summary

PSR-9 deals with the process by which security issues are submitted or reported to project maintainers.
PSR-10 describes a machine-readable format for disclosing security issues to users.
Roave/SecurityAdvisories Prevents the installation of packages with known security vulnerabilities.
FriendsOfPHP/security-advisories provides tools for identifying dependencies with known security issues.

Encryption when you need decryption. Hash when you don't (e.g: passwords)
Encryption provides confidentiality, AEAD aims to go further.
Message authentication/integrity checksum is usually a hashing problem, rather than encryption.
Scott discusses some encryption pitfalls and how a simple operation like == can become very complex to implement securely without becoming vulnerable to side-channel attacks. Encryption is hard - don't roll your own. Leave it to the specialists.
RFC: OpenSSL AEAD support
Always hash passwords with a slow hash function like bcrypt, scrypt or argon2 in libsodium. Fast hash functions like sha-2 are more vulnerable to brute-force attacks.
hash_pbkdf2() can be used to slow down your hash process to guard against brute-force by creating a bottleneck for an attacker. Don't DDOS your own server though: Use rate-limiting to avoid creating a DDOS vector.

Don't do a mass mailing and require a password reset from everyone: This implies a breach has taken place.
Phased update - upgrade your user base gradually:
- Re-hash passwords using a new algorithm in the background each time a user logs in. Mark the user as re-hashed each time.
- As users log in, force a password reset.
bcrypt all the md5 hashes and make your hashing algorithm bcrypt(md5($password))

libsodium is a C library implementing best-in-class cryptographic and hashing algorithms
Safe from side-channel and cache-timing attacks
There are plans to move to libsodium implementations of built-in crypto function in PHP >= 7.2
mcrypt is deprecated in PHP 7.1