Hawkynt

Crypto-1

Proprietary stream cipher used in NXP MIFARE Classic cards, reverse-engineered by cryptographic community. Uses 48-bit LFSR with nonlinear filter function. Cryptographically broken with multiple practical attacks published.

Properties

Property	Value
Category	Stream Ciphers
Sub-category	Stream Cipher
Security status	❌ Broken
Complexity	Intermediate
Inventor	NXP Semiconductors (proprietary design)
Year	1994
Origin	🇳🇱 Netherlands
Source	algorithms/stream/crypto1.js

Parameters

Parameter	Supported values
Key sizes	6 bytes (48 bits)
Nonce sizes	0 bytes (0 bits)

Security

Status: ❌ Broken

Known vulnerabilities

Issue	Description	Mitigation
Key Recovery Attack	Multiple practical key recovery attacks allow extracting 48-bit keys in seconds	Do not use - algorithm is fundamentally broken
Weak PRNG	Predictable keystream generation allows statistical attacks	Algorithm cannot be fixed - replace with secure alternative
Correlation Attacks	Linear correlations in LFSR output enable cryptanalytic attacks	Fundamental design flaw - use modern stream ciphers instead

Documentation

• Crypto-1 Cryptanalysis
• MIFARE Classic Security Analysis
• Dismantling MIFARE Classic

References

• crapto1 Reference Library (Proxmark3)
• mfcuk crypto1 Implementation

Test vectors

1 vector ship with this algorithm and run in the test suite. Byte values are hexadecimal.

Vector 1 — Crypto-1 Test Vector (Educational)

Field	Value
key	000102030405
input	00000000
expected	4e8485a0

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