ChaChaRandom class

ChaCha20-based SecureRandom implementation.

The throughput is up to about 0.25 GB of random data per second. This is over 100 times faster than Random.secure on many platforms.

Current algorithm

The default behavior is:

  • 12 rounds of ChaCha. No key extraction attack has been proposed against ChaCha with more than 6 rounds so the choice has a good margin of safety.
  • 256-bit secret key is mixed (XOR) with numbers from Random.secure at least once every 8192 blocks. This is also done if more than 10 milliseconds has passed since the last reseed event.
  • After a block has been computed, the block counter is incremented.
  • After a block has been computed, the last 128 bits of the secret key is immediately mixed (XOR) with the first 128 bits of the state. The first 128-bits of the state are then zeroed and skipped. This provides backtracking resistance.
  • State bits are erased after they have been read so a memory dump won't reveal them.

Example

import 'package:cryptography/random.dart';

void main() {
  final random = SecureRandom.fast;
  final x = random.nextInt(100);
  print('x = $x');
}
Inheritance

Constructors

ChaChaRandom({int rounds = defaultRounds, int maxBlocksBeforeReseed = defaultMaxBlocksBeforeReseed, Duration? maxDurationBeforeReseed = defaultMaxDurationBeforeReseed})
ChaChaRandom.forTesting({int seed = 0})

Properties

hashCode → int
The hash code for this object.
no setterinherited
isSecure → bool
Tells whether the algorithm is cryptographically secure and the initial entropy is from Random.secure.
no setteroverride
maxBlocksBeforeReseed → int
Maximum number of 64 byte blocks since the last reseed before the random number generator must be reseeded.
final
maxDurationBeforeReseed → Duration?
Maximum elapsed time since the last reseed before the random number generator must be reseeded.
final
reseedCount → int
no setter
rounds → int
Number of ChaCha rounds.
final
runtimeType → Type
A representation of the runtime type of the object.
no setterinherited

Methods

nextBool() → bool
Generates a random boolean value.
inherited
nextDouble() → double
Generates a non-negative random floating point value uniformly distributed in the range from 0.0, inclusive, to 1.0, exclusive.
inherited
nextInt(int max) → int
Generates a non-negative random integer uniformly distributed in the range from 0, inclusive, to max, exclusive.
inherited
nextUint32() → int
Returns a random unsigned 32-bit integer.
override
nextUint52([int? max]) → int
Returns a random cross-platform unsigned 52-bit integer.
inherited
noSuchMethod(Invocation invocation) → dynamic
Invoked when a nonexistent method or property is accessed.
inherited
reset() → void
override
toString() → String
A string representation of this object.
override

Operators

operator ==(Object other) → bool
The equality operator.
inherited

Constants

defaultMaxBlocksBeforeReseed → const int
Default value for maxBlocksBeforeReseed.
defaultMaxDurationBeforeReseed → const Duration
Default value for maxDurationBeforeReseed.
defaultRounds → const int
Default value for rounds.