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Checksums

For data integrity without security requirements. These are fast but NOT cryptographically secure. An attacker can easily make data with any checksum they want.

CRC32​

local CRC32 = Cryptography.Checksums.CRC32

CRC32(Message: buffer, Mode: "Jam" | "Iso"?, Hex: boolean?) -> number​

Computes a 32 bit CRC.

-- Default mode, returns number
local Checksum = CRC32(buffer.fromstring("data"))
print(Checksum) -- e.g., 3632233996

-- Return as hex string
local HexChecksum = CRC32(buffer.fromstring("data"), nil, true)
print(HexChecksum) -- e.g., "d87f7e0c"

-- JAM mode (different polynomial finalization)
local JamChecksum = CRC32(buffer.fromstring("data"), "Jam")

-- ISO mode
local IsoChecksum = CRC32(buffer.fromstring("data"), "Iso")

Modes:

  • Default: Standard CRC 32 (Ethernet, ZIP, PNG)
  • "Jam": CRC 32/JAMCRC (inverted, no final XOR)
  • "Iso": CRC 32/ISO HDLC

Use CRC32 for file integrity, error detection, and anywhere you need a fast checksum. Do not use it for security.

Adler​

local Adler = Cryptography.Checksums.Adler

Adler(Message: buffer) -> number​

Computes an Adler 32 checksum.

local Checksum = Adler(buffer.fromstring("data"))
print(Checksum)

Adler 32 is faster than CRC32 but has weaker error detection properties. It is used in zlib compression. The checksum is computed as two running sums modulo 65521.

When to Use What​

Use CaseAlgorithm
File integrity (no adversary)CRC32
zlib/deflate compatibilityAdler
Maximum speed, weak detectionAdler
Hash tables, bloom filtersXXH32 or MurMur
Any security requirementSHA256, BLAKE3, or HMAC
Not for Security

These checksums are easily forgeable. If someone might tamper with your data, use a cryptographic hash (SHA256, BLAKE3) or a MAC (HMAC, BLAKE3 DigestKeyed).