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EME

EME (ECB-Mask-ECB) is a wide-block tweakable cipher mode that can handle variable-length inputs while preserving format. It uses a three-round construction: ECB encrypt, mask with universal hash, then ECB encrypt again. Primarily used for format-preserving encryption applications.

Properties

Property	Value
Category	Cipher Modes
Sub-category	Wide-Block Tweakable Mode
Security status	🧪 Experimental
Complexity	Research
Inventor	Shai Halevi, Phillip Rogaway
Year	2003
Origin	🇺🇸 United States
Source	algorithms/modes/eme.js

Capabilities

Flag	Value
RequiresIV	No

Security

Status: 🧪 Experimental

Known vulnerabilities

Issue	Description	Mitigation
Research Status	EME mode is primarily used in specialized format-preserving encryption applications and has limited real-world deployment.	—
Implementation Complexity	Requires careful implementation of universal hash functions and proper masking operations.	—

Documentation

• EME Original Paper
• Wide-Block Encryption
• Format-Preserving Encryption

References

• Academic Implementation
• FPE Libraries

Test vectors

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

Vector 1 — EME round-trip test - single block

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

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