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Leviathan

Large-state eSTREAM candidate with 4096-bit internal state. Uses 8 parallel LFSRs with nonlinear S-box filter for high security margin. Designed by David McGrew but eliminated in Phase 2 due to performance concerns.

Properties

Property	Value
Category	Stream Ciphers
Sub-category	Stream Cipher
Security status	🎓 Educational Only
Complexity	Advanced
Inventor	David McGrew
Year	2005
Origin	🇺🇸 United States
Source	algorithms/stream/leviathan.js

Parameters

Parameter	Supported values
Key sizes	32 bytes (256 bits)
Block sizes	1 byte (8 bits) to 65536 bytes (524288 bits)

Security

Status: 🎓 Educational Only

Known vulnerabilities

Issue	Description	Mitigation
Performance Issues	Large state causes poor performance, eliminated from eSTREAM Phase 2	—
Cryptanalytic Concerns	Various cryptanalytic issues identified during evaluation	—

Documentation

• eSTREAM Leviathan Page
• eSTREAM Project

References

• Leviathan NESSIE Submission Archive (Spec and Reference Source)
• NESSIE Project Archive

Test vectors

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

Vector 1 — Leviathan Test Vector - Basic

Source: Educational implementation test

Field	Value
key	000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f
iv	101112131415161718191a1b1c1d1e1f202122232425262728292a2b2c2d2e2f
input	4c617267652073746174652074657374
expected	c66722497fc085671eb4ad666198fc1d

Vector 2 — Leviathan Test Vector - All Zeros

Source: Educational implementation test

Field	Value
key	0000000000000000000000000000000000000000000000000000000000000000
iv	0000000000000000000000000000000000000000000000000000000000000000
input	4e756c6c206b6579207465737470
expected	2d160f0f4308061a431706101713

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