Paper 2025/547

Improved Cryptanalysis of FEA-1 and FEA-2 using Square Attacks

Abhishek Kumar, ZF India Private Limited, India
Amit Kumar Chauhan, QNu Labs Private Limited, Bengaluru, India
Somitra Kumar Sanadhya, Indian Institute of technology Jodhpur, Jodhpur, India
Abstract

This paper presents a security analysis of the South Korean Format-Preserving Encryption (FPE) standards FEA-1 and FEA-2. In 2023, Chauhan \textit{et al.} presented the first third-party analysis of FEA-1 and FEA-2 against the square attack. The authors proposed new distinguishing attacks covering up to three rounds of FEA-1 and five rounds of FEA-2, with a data complexity of 28 plaintexts. Additionally, using these distinguishers, they presented key recovery attacks for four rounds of FEA-1 and six rounds of FEA-2, for 192-bit and 256-bit key sizes. The complexities of both the four-round FEA-1 and six-round FEA-2 key recovery attacks are . In this work, we successfully extend the number of rounds attacked for both FEA-1 and FEA-2, using the square attack technique. Specifically, we present a four-round distinguishing attack against FEA-1 and six-round distinguishing attack against FEA-2. The data complexities of these distinguishers are plaintexts. Furthermore, we apply these distinguishers to perform key recovery attacks on five rounds of FEA-1 and seven rounds of FEA-2, targeting the 256-bit key size. The time complexities of the presented key recovery attacks are .

Metadata
Available format(s)
PDF
Category
Attacks and cryptanalysis
Publication info
Preprint.
Keywords
Format Preserving EncryptionFEA-1FEA-2Square attackRound Function
Contact author(s)
abhishek kumar iitrpr @ gmail com
akcindia macs @ gmail com
somitra @ iitj ac in
History
2025-03-25: approved
2025-03-25: received
See all versions
Short URL
https://ia.cr/2025/547
License
Creative Commons Attribution
CC BY

BibTeX

@misc{cryptoeprint:2025/547,
      author = {Abhishek Kumar and Amit Kumar Chauhan and Somitra Kumar Sanadhya},
      title = {Improved Cryptanalysis of {FEA}-1 and {FEA}-2 using Square Attacks},
      howpublished = {Cryptology {ePrint} Archive, Paper 2025/547},
      year = {2025},
      url = {https://eprint.iacr.org/2025/547}
}
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