 # Randomness and Entropy in Node and Electron

Randomness is a hard problem for computers. For this reason most functions that generate randomness are not considered cryptographically secure. That means that it is possible that an attacker can take a good guess at what number a non-secure randomness generator generated.

## How can randomness be attacked?

Many non-secure randomness (or entropy) generators would do something similar to the following:

```function getRandom(timestamp, maxNumber){
// Take the deterministic hash of the timestamp
const hashedTime = sha256(timestamp)
// Reduce the hash to within the range [0, maxNumber)
return hashedTime % maxNumber
}```

This function (while ignoring some implementation details of modulus math by such a large number) will return random numbers that are based on the timestamp input, which is called the seed. If I pass in many different timestamps, the various outputs would appear random. This is an example of a weak psuedo-random number generator.

A weak psuedo-random number generator works perfectly fine if one is trying to:

• Create sample data for an application
• Write a video game engine
• etc …

Weak psuedo-randomness can be catastrophically dangerous if one is trying to:

• Generate Bitcoin keys
• Generate passwords or salts
• etc …

## Strong Psuedo-Randomness (Cryptographically Secure)

A software-only system like Qvault can at best generate strong psuedo-random data because we are working on deterministic systems. Without an outside source of entropy (like someone rolling a dice and telling the computer each output) we are at the mercy of psuedo-randomness.

## crypto.randomBytes()

Node’s built in crypto.randomBytes is a cryptographically secure random number generator that is based on openssl. Depending on the operating system of the user, randomBytes will use

/dev/urandom (unix)

or

CryptoGenRandom (windows)

While still psuedo-random sources, the important thing is that they are not guessable by an attacker. In other words, after using crypto.randomBytes() to generate a recovery code in Qvault, an attacker can’t recreate that code.

## What do I do?

In short, use crypto.randomBytes() whenever you need raw random bytes. If you need a random number within a range, for example, a random number between 0-9, then use a non-biased function that uses crypto.randomBytes() as the source of entropy. For example:

node-random-number-csprng

Good luck, and always check the source!

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By Lane Wagner

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