Crypto.getRandomValues()
method lets you get cryptographically strong random values. The array given as the parameter is filled with random numbers (random in its cryptographic meaning).
To guarantee enough performance, implementations are not using a truly random number generator, but they are using a pseudo-random number generator seeded with a value with enough entropy. The pseudo-random number generator algorithm (PRNG) may vary across user agents , but is suitable for cryptographic purposes. Implementations are required to use a seed with enough entropy, like a system-level entropy source.
getRandomValues()
is the only member of the
Crypto
interface which can be used from an insecure context.
typedArray = cryptoObj.getRandomValues(typedArray);
typedArray
TypedArray
, that is an
Int8Array
，
Uint8Array
，
Int16Array
，
Uint16Array
，
Int32Array
，或
Uint32Array
. All elements in the array are overwritten with random numbers.
The same array passed as
typedArray
but with its contents replaced with the newly generated random numbers. Note that
typedArray
is modified in-place, and no copy is made.
This method can throw an exception under error conditions.
DOMException
(name:
QuotaExceededError
)
The requested length exceeds 65,536 bytes.
不使用
getRandomValues()
to generate encryption keys. Instead, use the
generateKey()
method. There are a few reasons for this; for example,
getRandomValues()
is not guaranteed to be running in a secure context.
There is no minimum degree of entropy mandated by the Web Cryptography specification. User agents are instead urged to provide the best entropy they can when generating random numbers, using a well-defined, efficient pseudorandom number generator built into the user agent itself, but seeded with values taken from an external source of pseudorandom numbers, such as a platform-specific random number function, the Unix
/dev/urandom
device, or other source of random or pseudorandom data.
/* Assuming that window.crypto.getRandomValues is available */
var array = new Uint32Array(10);
window.crypto.getRandomValues(array);
console.log("Your lucky numbers:");
for (var i = 0; i < array.length; i++) {
console.log(array[i]);
}
| 规范 | 状态 | 注释 |
|---|---|---|
| Web Cryptography API | 推荐 | 初始定义 |
| 桌面 | 移动 | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
getRandomValues()
|
Chrome 11 | Edge 12 | Firefox 26 | IE 11 | Opera 15 | Safari 6.1 | WebView Android ≤37 | Chrome Android 18 | Firefox Android 26 | Opera Android 14 | Safari iOS 6.1 | Samsung Internet Android 1.0 |
完整支持
Window.crypto
to get a
Crypto
对象。
Math.random
, a non-cryptographic source of random numbers.
Crypto
getRandomValues()