Created
July 12, 2012 05:00
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Random alphanumeric (base-62) strings in Node.js, cryptographically strong
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| var bases = require('bases'); | |
| var crypto = require('crypto'); | |
| // Returns a base-62 (alphanumeric only) string of the given length: | |
| function randomStr(length) { | |
| // We generate a random number in a space at least as big as 62^length, | |
| // and if it's too big, we just retry. This is still statistically O(1) | |
| // since repeated probabilities less than one converge to zero. Hat-tip to | |
| // a Google interview for teaching me this technique! ;) | |
| // The native randomBytes() returns an array of bytes, each of which is | |
| // effectively a base-256 integer. We derive the number of bytes to | |
| // generate based on that, but note that it can overflow after ~150: | |
| var maxNum = Math.pow(62, length); | |
| var numBytes = Math.ceil(Math.log(maxNum) / Math.log(256)); | |
| if (numBytes === Infinity) { | |
| throw new Error('Length too large; caused overflow: ' + length); | |
| } | |
| do { | |
| var bytes = crypto.randomBytes(numBytes); | |
| var num = 0 | |
| for (var i = 0; i < bytes.length; i++) { | |
| num += Math.pow(256, i) * bytes[i]; | |
| } | |
| } while (num >= maxNum); | |
| return bases.toBase62(num); | |
| } | |
| for (var i = 1; i < 80; i++) { | |
| console.log(randomStr(i)); | |
| } |
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| n | |
| Fj | |
| Zuf | |
| Qewt | |
| YzKp2 | |
| ARo7Ym | |
| 629xow7 | |
| vPdGF8Vx | |
| MQlxlgsOU | |
| EhIuYD3r32 | |
| ro0nwTnz44w | |
| gHjfLjflzqgY | |
| tTyr1fy62GKYy | |
| BBUuD9KhkyICOA | |
| A36xHiZIqG0ksKS | |
| X9DdiWElSUQEMEyG | |
| sskrmb6LWS4Smsimg | |
| Aw49rNTFN6IC6Qy0uY | |
| AyXDmmjcqWWmmY8uuKM | |
| TiK0Ps8ra82igYmaYsmM | |
| EwKuPgb8U8mOAS22YYiw0 | |
| xihPfDRhiSsgGgUAikoCOC | |
| uB2uAuJFBIMYYY8S6sSG6kE | |
| mW4DzyWnOokEoYSUgCiiCas2 | |
| XnxSqxTHmCIAsigWusOk6YCyA | |
| lodRWjHBGC0cY2MCqKoIQqAWua | |
| 8EZttmGxXigkmsAS0aUSwMsWkUm | |
| L16lxbE8kSoO6WacQiMsUCQcC6ao | |
| KQgZMStN28M8OUw6EwYUQYaOcoUQq | |
| IEzAddFN2m6owmQSKOYQCo0i0ySSeW | |
| ZMFFfJBLIkIckkqyg4kMYKggiSMQko | |
| a4ZLM7nQ0EKISKOEmiYwK6SCe20AA8gs | |
| xhGo4aDv1uqMIMIqewEI4oMOqCMw0WKg8 | |
| RZcQGuJDc28Ei4yEUe8AUWKUGIcMk2ogoe | |
| fHpcWD5LgsOQAMgcMsYkiwk2kKEYSakGo2M | |
| fufHNCLhcImqiOcMKGsssUaGe6GWw4gyaqUi | |
| MfPBmiig4UYKyogseMCmyi6s26yMwMkmq4qcI | |
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| LYUa50jMUCCiUsckCSW0ayKSYeuScweAIwSWGEkQS | |
| 4mxzCYXHYcaOCwo0ySGy64G4QsqQoYiWoyaKKukImA | |
| qCmIiARn4ks8OmEEMSqEeG2EAauoaUMko8SW86YSoWm | |
| glOL2pZQ1aOIMQakGwcEEcSqAWIqS0IuAyOC2Kwy84ws | |
| pdLVnjjUPesEYi6MsKUCSccQK0qeuYESGIOumY8E8AM6K | |
| OTAv8bD8YwI0OuUaGayOk6SAMMOYmi28OysM82SCs4qiam | |
| TVTQbMYf6gKsKSeyQWMmSqOwmEc6UekMECuWCoSQO6OE0MO | |
| 9melnBOB5SMcQ48WWGyEuOsIWqycUsYe02U4Kueoo0yAqcaI | |
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| oo4Rs3nr7EQmgWsakeSqGAqq8MugceKwoCEG2ScG2Kq2i0Uy2WIqkGI2yK | |
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| RU1l7PlUA0cyIuIIc6GsuImCSkUY0AMkeGgW4e8ges00cWky04umkiI4YaOuCO86 | |
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| ZxzQwlH7WuCMeauaOE2iG240gmCWgcqMyQCq02Iy4aEcE8Cw8wSUe6cguQUu0CMa0E6a | |
| P1lCXbizgiu84QwGUs26OSE8GOAGIomEComUggeuUco6GQmKk848o2yoOYmm8O8yAaswe | |
| 3v7gFZnXzOwGQYOMSWmWsYSuUMcosgUWO2CUGIG4we6Mm8c6UU2ykIikU4iAAmAYu88ckc | |
| shbsDxrTNIoeGiuGAGc468o2uQOIYmqce4Ga60uuwYK0yI6CEsYI6IQ4eCyMcCUkoMewYiE | |
| mGz5QRxKpMiUioIOkqKGIOiQEOWygKsYwUw08SOE2uAK4SQsmkeSqGS6QekOMMYUmKOgo2Oy | |
| 4i7wRnCXSoOeQWAQC8wKMaqY8yUQCyq8eiQ2S2EU2AAm0SKQKMiAqgiUaKCqIgKQwIUsAUgGu | |
| 8is6AP4KpqKeW2KO4eUmCyw2sgWAyooUA2QI66KMyyeqUKo6AOUKOwAAIKmqCIM6AWO8MwSsY | |
| J7rLm8GzYYs0GkOgwMyU6Y4YcyO8EW6CaG2UUsGQ6kiA6SkIgmcUmWAiOkwY0MwkeWywk4W4Ic0 | |
| 1C5lu0V4AgwoSIsU2QQA4euasiiUmcaIgCiaSqWKKos0s6MgwUUUe6ewQm8CU8wWu8gSmIqKqGIU | |
| eiiPQgyJEIGMYUcISYy8aEYUcewSUGocAgOIcsyYiSMUu4QiQcc8kyyEUqyom4OAs00cmEAg0aOce | |
| lq3CoBvrrMQOmS2YckwYcgqwOuQ4gEyq2GO8Ge4Amyw2AUW4IMIu6oig0My6sGuaOWA0EiECeUOoku | |
| iik2dMq4jCYyUWyUsm44EoMyMCauyEEsqE8EYSoEkyW820KQoSgwIyqKIAWG0KcYsCASo2WUcW4WmAa |
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they are still random not matter what :)