paragonie / seedspring
Seeded, deterministic random number generator
Installs: 132 197
Dependents: 1
Suggesters: 0
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Watchers: 7
Forks: 4
Open Issues: 0
Requires
- php: >= 5.6
- ext-openssl: *
- paragonie/constant_time_encoding: ^1|^2|^3
- paragonie/random_compat: >=2
Requires (Dev)
- phpunit/phpunit: ^5|^6|^7|^8|^9
- vimeo/psalm: ^1|^2|^3|^4
README
Seeded, Deterministic PRNG (based on AES-CTR instead of LCG) (Requires PHP 7 or random_compat)
Security Warning
This is not meant to replace random_bytes(). Think of this as an improvement
to srand() + rand(). Do not use this for security purposes.
Installing
composer require paragonie/seedspring
Usage
use \ParagonIE\SeedSpring\SeedSpring; // For example $sharedSeed = str_repeat("\x80", 16); $rng = new SeedSpring($sharedSeed); $data = $rng->getBytes(1024); $int = $rng->getInt(1, 100);
Motivation
A cryptographically secure pseudorandom number generator, such as random_int(),
is wonderful for security purposes. However, there are situations where you need
to generate a deterministic, pseudorandom byte stream on two devices from a
shared seed. (e.g. something like Minecraft's world generator).
PHP's native seedable (and insecure) RNGs, rand() and mt_rand(), only
support a 32-bit integer seed, which severely limits the possible outputs. Our
deterministic RNG supports up to 2^128 possible outputs, since it's based on a
128-bit block cipher.
Our implementation uses AES-128-CTR to turn a finite, 128-bit key into an practically endless stream of random bytes.
It will repeat after 2^132 bytes of output. You should consider rekeying after 2^66 bytes.
For anything security-sensitive, you should rekey after 2^39 bytes. This is because the probability of predicting successive blocks becomes unacceptably high for security operations.