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The k6/crypto module provides common hashing and cryptographic functionality.

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Import

import crypto from 'k6/crypto';

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Hash Functions

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createHash()

Creates a Hasher object that can be fed with data repeatedly to generate hash digests.
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algorithm
string
required
The hashing algorithm to use. One of: "md4", "md5", "sha1", "sha256", "sha384", "sha512", "sha512_224", "sha512_256", "ripemd160".
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return
Hasher
A Hasher object with update(data) and digest(encoding) methods.
import crypto from 'k6/crypto';

export default function () {
  console.log(crypto.sha256('hello world!', 'hex'));
  const hasher = crypto.createHash('sha256');
  hasher.update('hello ');
  hasher.update('world!');
  console.log(hasher.digest('hex'));
}
Output: 
INFO[0000] 7509e5bda0c762d2bac7f90d758b5b2263fa01ccbc542ab5e3df163be08e6ca9
INFO[0000] 7509e5bda0c762d2bac7f90d758b5b2263fa01ccbc542ab5e3df163be08e6ca9

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createHMAC()

Creates an HMAC hashing object for generating signed hash digests.
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algorithm
string
required
The hashing algorithm. One of: "md4", "md5", "sha1", "sha256", "sha384", "sha512", "sha512_224", "sha512_256", "ripemd160".
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secret
string | ArrayBuffer
required
A shared secret used to sign the data.
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return
Hasher
A Hasher object with update(data) and digest(encoding) methods.
import crypto from 'k6/crypto';

export default function () {
  console.log(crypto.hmac('sha256', 'a secret', 'my data', 'hex'));
  const hasher = crypto.createHMAC('sha256', 'a secret');
  hasher.update('my ');
  hasher.update('data');
  console.log(hasher.digest('hex'));
}
Output: 
INFO[0000] 82f669c8fde13aef6d6977257588dc4953dfac505428f8fd6b52e19cd96d7ea5
INFO[0000] 82f669c8fde13aef6d6977257588dc4953dfac505428f8fd6b52e19cd96d7ea5

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Direct Hash Functions

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md5()

Computes MD5 hash of input data.
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input
string | ArrayBuffer
required
The input string or ArrayBuffer to hash.
​
outputEncoding
string
required
Output encoding: "base64", "base64url", "base64rawurl", "hex", or "binary".
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return
string | Array
Hash digest as string or array of integers (for binary encoding).
import crypto from 'k6/crypto';

export default function () {
  let hash = crypto.md5('hello world!', 'hex');
  console.log(hash);
  const binArray = [104, 101, 108, 108, 111, 32, 119, 111, 114, 108, 100, 33];
  hash = crypto.md5(new Uint8Array(binArray).buffer, 'hex');
  console.log(hash);
}
Output: 
INFO[0000] fc3ff98e8c6a0d3087d515c0473f8677
INFO[0000] fc3ff98e8c6a0d3087d515c0473f8677

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sha256()

Computes SHA-256 hash of input data.
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input
string | ArrayBuffer
required
The input string or ArrayBuffer to hash.
​
outputEncoding
string
required
Output encoding: "base64", "base64url", "base64rawurl", "hex", or "binary".
​
return
string | Array
Hash digest as string or array of integers (for binary encoding).
import crypto from 'k6/crypto';

export default function () {
  let hash = crypto.sha256('hello world!', 'hex');
  console.log(hash);
  const binArray = [104, 101, 108, 108, 111, 32, 119, 111, 114, 108, 100, 33];
  hash = crypto.sha256(new Uint8Array(binArray).buffer, 'hex');
  console.log(hash);
}
Output: 
INFO[0000] 7509e5bda0c762d2bac7f90d758b5b2263fa01ccbc542ab5e3df163be08e6ca9
INFO[0000] 7509e5bda0c762d2bac7f90d758b5b2263fa01ccbc542ab5e3df163be08e6ca9

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Other Hash Functions

All hash functions follow the same signature as md5() and sha256():

md4()

MD4 hashing algorithm

sha1()

SHA-1 hashing algorithm

sha384()

SHA-384 hashing algorithm

sha512()

SHA-512 hashing algorithm

sha512_224()

SHA-512/224 hashing algorithm

sha512_256()

SHA-512/256 hashing algorithm

ripemd160()

RIPEMD-160 hashing algorithm

hmac()

HMAC with any supported algorithm

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Random Generation

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randomBytes()

Generates cryptographically random bytes.
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int
integer
required
The length of the returned ArrayBuffer.
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return
ArrayBuffer
An ArrayBuffer with cryptographically random bytes.
import crypto from 'k6/crypto';

export default function () {
  const bytes = crypto.randomBytes(42);
  const view = new Uint8Array(bytes);
  console.log(view); // [156, 71, 245, 191, 56, ...]
}
Use randomBytes() for cryptographically secure random data. For non-cryptographic randomness, use Math.random().

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Output Encodings

All hash functions support these output encodings:
  • "hex" - Hexadecimal string (most common)
  • "base64" - Standard base64 encoding
  • "base64url" - URL-safe base64 encoding
  • "base64rawurl" - URL-safe base64 without padding
  • "binary" - Array of integers (0-255)

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Use Cases

Generate HMAC signatures for API authentication:
const signature = crypto.hmac('sha256', API_SECRET, requestBody, 'hex');
Hash passwords before sending (though use bcrypt/argon2 in production):
const hashedPassword = crypto.sha256(password, 'hex');
Verify file or data integrity:
const checksum = crypto.md5(fileData, 'hex');
Generate random tokens or IDs:
const token = crypto.randomBytes(32);
const tokenHex = new Uint8Array(token).reduce((str, byte) => 
  str + byte.toString(16).padStart(2, '0'), '');
MD4 and MD5 are cryptographically broken. Use them only for non-security purposes like checksums. For security, use SHA-256 or higher.

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