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Tnepres

Tnepres is a 128-bit 32-round block cipher based on Serpent. Due to endianness confusion in AES submission test vectors, Tnepres is a byte-swapped version using big-endian byte order instead of little-endian.

Properties

Property	Value
Category	Block Ciphers
Sub-category	Block Cipher
Security status	🎓 Educational Only
Complexity	Advanced
Inventor	Ross Anderson, Eli Biham, Lars Knudsen
Year	1998
Origin	🇬🇧 United Kingdom
Source	algorithms/block/tnepres.js

Parameters

Parameter	Supported values
Key sizes	16 bytes (128 bits) to 32 bytes (256 bits) in steps of 8 bytes
Block sizes	16 bytes (128 bits)

Security

Status: 🎓 Educational Only

Known vulnerabilities

Issue	Description	Mitigation
Endianness Confusion	Tnepres resulted from byte order confusion in original AES submission. Use Serpent for production.	Use corrected Serpent cipher instead of Tnepres

Documentation

• Serpent Algorithm Specification
• BouncyCastle Tnepres Implementation

References

• BouncyCastle Serpent Base
• Serpent vs Tnepres Explanation

Test vectors

13 vectors ship with this algorithm and run in the test suite. Byte values are hexadecimal.

Vector 1 — Tnepres test vector #1 (256-bit key, zero plaintext)

Field	Value
key	0000000000000000000000000000000000000000000000000000000000000000
input	00000000000000000000000000000000
expected	8910494504181950f98dd998a82b6749

Vector 2 — Tnepres test vector #2 (128-bit key, bit 0 set)

Field	Value
key	00000000000000000000000000000000
input	80000000000000000000000000000000
expected	10b5ffb720b8cb9002a1142b0ba2e94a

Vector 3 — Tnepres test vector #3 (128-bit key, bit 39 set)

Field	Value
key	00000000000000000000000000000000
input	00000000008000000000000000000000
expected	4f057a42d8d5bd9746e434680ddcd5e5

Vector 4 — Tnepres test vector #4 (128-bit key, bit 63 set)

Field	Value
key	00000000000000000000000000000000
input	00000000000000000000400000000000
expected	99407bf8582ef12550886ef5b6f169b9

Vector 5 — Tnepres test vector #5 (192-bit key, bit 0 set)

Field	Value
key	000000000000000000000000000000000000000000000000
input	40000000000000000000000000000000
expected	d522a3b8d6d89d4d2a124fdd88f36896

Vector 6 — Tnepres test vector #6 (192-bit key, bit 74 set)

Field	Value
key	000000000000000000000000000000000000000000000000
input	00000000000200000000000000000000
expected	189b8ec3470085b3da97e82ca8964e32

Vector 7 — Tnepres test vector #7 (192-bit key, bit 67 set)

Field	Value
key	000000000000000000000000000000000000000000000000
input	00000000000000000000008000000000
expected	f77d868cf760b9143a89809510ccb099

Vector 8 — Tnepres test vector #8 (256-bit key, bit 4 set)

Field	Value
key	0000000000000000000000000000000000000000000000000000000000000000
input	08000000000000000000000000000000
expected	d43b7b981b829342fce0e3ec6f5f4c82

Vector 9 — Tnepres test vector #9 (256-bit key, bit 71 set)

Field	Value
key	0000000000000000000000000000000000000000000000000000000000000000
input	00000000000000000100000000000000
expected	0bf30e1a0c33ccf6d5293177886912a7

Vector 10 — Tnepres test vector #10 (256-bit key, bit 127 set)

Field	Value
key	0000000000000000000000000000000000000000000000000000000000000000
input	00000000000000000000000000000001
expected	6a7f3b805d2ddcba49b89770ade5e507

Vector 11 — Tnepres test vector #11 (128-bit key bit 0 set)

Field	Value
key	80000000000000000000000000000000
input	00000000000000000000000000000000
expected	49afbfad9d5a34052cd8ffa5986bd2dd

Vector 12 — Tnepres test vector #12 (192-bit key bit 86 set)

Field	Value
key	000000000000000000000000004000000000000000000000
input	00000000000000000000000000000000
expected	ba8829b1de058c4b48615d851fc74f17

Vector 13 — Tnepres test vector #13 (256-bit key bit 199 set)

Field	Value
key	0000000000000000000000000000000000000000000000000000000100000000
input	00000000000000000000000000000000
expected	89f64377bf1e8a46c8247044e8056a98

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