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XEX

XEX (XOR-Encrypt-XOR) is a tweakable block cipher construction that forms the foundation of the XTS disk encryption mode. It uses a simple but effective approach: XOR the plaintext with a tweak-derived mask, encrypt with a standard block cipher, then XOR again with the same mask. This provides strong tweakable encryption suitable for disk encryption.

Properties

Property	Value
Category	Cipher Modes
Sub-category	Tweakable Block Cipher
Security status	🛡️ Secure
Complexity	Intermediate
Inventor	Phillip Rogaway
Year	2004
Origin	🇺🇸 United States
Source	algorithms/modes/xex.js

Capabilities

Flag	Value
RequiresIV	No

Security

Status: 🛡️ Secure

Known vulnerabilities

Issue	Description	Mitigation
Superseded by XTS	XEX is now primarily used as the foundation for XTS mode rather than directly. XTS provides additional security improvements.	—
Single-Key Weakness	Pure XEX with a single key has some theoretical weaknesses that XTS addresses by using two independent keys.	—

Documentation

• XEX Original Paper
• IEEE 1619-2007 XTS
• NIST SP 800-38E

References

• XTS Implementation (XEX successor)
• Linux dm-crypt
• OpenSSL XTS

Test vectors

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

Vector 1 — XEX round-trip test - single block

Field	Value
key	2b7e151628aed2a6abf7158809cf4f3c
tweakKey	603deb1015ca71be2b73aef0857d7781
tweak	000102030405060708090a0b0c0d0e0f
input	6bc1bee22e409f96e93d7e117393172a
expected	(empty)

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