Crypto

Overview

This document describes a proposal for the window.crypto API.

Definitions

Cryptographically Random Values

A cryptographically random value is a value generated from a cryptographically strong pseudo-random number generator seeded with truly random values. In practice, implementations should generate cryptographically random values using well-established cryptographic pseudo-random number generators, such as RC4, seeded with high-quality entropy, such as from an operating-system entropy source (e.g., /dev/urandom). This document provides no lower-bound on the information theoretic entropy present in cryptographically random values, but implementations should make a best effort to provide as much entropy as practicable.

Interface Crypto

interface Crypto {
  void getRandomValues(in ArrayBufferView array);
};

partial interface Window {
  readonly attribute Crypto crypto;
};

The getRandomValues(array) must run the following steps:

1. array is an ArrayBufferView. If array is not of an integer type (i.e., Int8Array, Uint8Array, Int16Array, Uint16Array, Int32Array, or Uint32Array), throw a TypeMismatchError and abort these steps.
2. If array's length is greater than 65536, throw a QuotaExceededError and abort these steps.
3. Overwrite all elements of array with cryptographically random values of the appropriate type.