1.0.1 • Public • Published

hat-Compatible CSPRNG

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This is a node.js package that implements hat's main API, but uses a cryptographically secure pseudo-random number generator to generate the random identifiers. This is especially beneficial when using older versions of V8 that exhibit this bug.

In our use cases, cryptohat takes up to 3x more time to produce a random string than hat. However, cryptohat also exposes an alternative API that produces random numbers up to 2x faster than hat, while still using a CSPRNG.


This package should work on any reasonably modern browser or node.js version.

Every commit is tested using continuous integration on node.js 0.10 and above. Releases are also tested against the most recent versions of Chrome, Firefox, Safari, and Internet Explorer.


Install using npm or bower.

npm install cryptohat@1.x --save
bower install cryptohat@1.x --save


cryptohat implements the hat(bits, base) API. The function takes in the desired number of bits of randomness and the base/radix that will be used to represent the returned random number, and returns a string. The returned strings are guaranteed to have the same length for a given bits/base combination. As long as you don't need the hat.rack method, cryptohat can be used as a drop-in replacement.

var hat = require('cryptohat');
hat();  // '39a00e331acce7516a8ea69b85e191f0'
hat();  // '00549f7401ac0ba9ea1b791f50bc7b1e'
hat(53, 10);  // '6738095220277140'

Pass in zero (0) for the base argument to get a number. This is significantly faster than obtaining a string and converting it into a number. Keep in mind that JavaScript numbers can accurately represent integers of at most 53 bits.

var cryptohat = require('cryptohat');
cryptohat(53, 0);  // 6738095220277140
cryptohat(32, 0);  // 3840742823
cryptohat(63, 0);  // RangeError: JavaScript numbers can accurately represent at most 53 bits

For maximum throughput, use the cryptohat.generator API. It takes exactly the same arguments as the hat API, but it returns a generator function. Calling the function yields random numbers or identifiers.

var rng1 = cryptohat.generator(53, 0);
rng1();  // 4438236126178078
rng1();  // 187896805323588
var rng2 = cryptohat.generator(32, 10);
rng2();  // '0053668130'
rng2();  // '1939036909'


After cloning the repository, install the dependencies.

npm install
node node_modules/.bin/bower install

Make sure the tests pass after making a change.


When adding new functionality, make sure it has good test coverage and that it does not regress the code's performance.

SKIP_BENCHMARKS=1 npm run cov
npm test

When adding new functionality, also make sure that the documentation looks reasonable.

npm run doc

When modifying code around or inside feature detection blocks (combinations of if and typeof), make sure the tests pass at least in Chrome and Firefox, by opening test/index.html in the browsers.

open test/index.html  # On OSX. 
xdg-open test/index.html  # On Linux. 

When testing against a browser in a VM (e.g., for Internet Explorer), spawn a local Web server inside the source tree and visit it inside the VM (e.g.,

node node_modules/.bin/http-server

If you submit a pull request, Travis CI will run the test suite against your code on the node versions that we support. Please fix any errors that it reports.


Copyright (c) 2016 Heap Inc., released under the MIT license.



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