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VMPC

Variably Modified Permutation Composition stream cipher using RC4-like structure with enhanced mixing function P[P[P[s]]+1]. Designed as improved RC4 alternative with stronger security properties.

Properties

Property	Value
Category	Stream Ciphers
Sub-category	Stream Cipher
Security status	🧪 Experimental
Complexity	Intermediate
Inventor	Bartosz Zoltak
Year	2004
Origin	Not specified
Source	algorithms/stream/vmpc.js

Parameters

Parameter	Supported values
Key sizes	1 byte (8 bits) to 256 bytes (2048 bits)
Nonce sizes	1 byte (8 bits) to 768 bytes (6144 bits)

Security

Status: 🧪 Experimental

Known vulnerabilities

Issue	Description	Mitigation
Limited Cryptanalysis	VMPC has received less cryptanalytic attention compared to established stream ciphers	Use only after thorough security review for your specific use case

Documentation

• VMPC Specification
• eSTREAM Submission

References

• BouncyCastle VMPCEngine.java Implementation
• Author’s Own C/Pascal/Assembler Implementations

Test vectors

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

Vector 1 — BouncyCastle Test Vector - First 256 bytes (verified against Java implementation)

Field	Value
key	9661410ab797d8a9eb767c21172df6c7
iv	4b5c2f003e67f39557a8d26f3da2b155
input	00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000
expected	a82479f512e604148db1548cd194702e de20e787fe248a543efe139c071b78ac 7c2af5a8272d0ed09c649ecdfdecec20 454c8a7f675ad8816ba569dab29b7079 d57a2f1279ebd9aefb67a8d6403af44c 2d8c4327d09ad4f35a0c967d7dc31319 c7dab130e7eb69c9b71518011226b4d2 8f4927249f0103721714dca5f7c62040 58e11c87eb014dab75041cc2d096a7f7 719081c3d7292d5a9c6ca4aa59d386ca d51db9efdbe45a8293bd34ee876fc7e9 94653ab726f83b82abdaeba885c7050b 9bf9b74ff64ce0f64094a80fecbf0481 c1e0d2e8cab65dc3b8fdecb7720c860f a143eff4f36fa8f729e791d1a6be657b acac49815467c2ca4a3951c0b8fc66a4

Vector 2 — BouncyCastle Test Vector - First 32 keystream bytes

Field	Value
key	9661410ab797d8a9eb767c21172df6c7
iv	4b5c2f003e67f39557a8d26f3da2b155
input	0000000000000000000000000000000000000000000000000000000000000000
expected	a82479f512e604148db1548cd194702ede20e787fe248a543efe139c071b78ac

Vector 3 — DarkCrypt Vmpc - 128-byte keystream (key=00..3F, IV=00)

Field	Value
key	000102030405060708090a0b0c0d0e0f 101112131415161718191a1b1c1d1e1f 202122232425262728292a2b2c2d2e2f 303132333435363738393a3b3c3d3e3f
iv	00
input	00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000 00000000000000000000000000000000
expected	291626f81795b6895ec89d4fd2dbb119 5ba0a901161bb1ba0b8e3f5ec14187ae 94ab8fe2e9a564b8e9c1345cfede1796 8aba3029130327bdfec2b641134b30c3 10dc2991128094cfeadb960e65c7b9d5 eb1705b5401de5a8fdd966b6d3fd6d3d 212410385fc1b834ac3b3f3268ea7c2a ac731ada2e113afb7800bdc541cbbe92

Vector 4 — DarkCrypt Vmpc - enc of 00..3F (key=00..3F, IV=00)

Field	Value
key	000102030405060708090a0b0c0d0e0f 101112131415161718191a1b1c1d1e1f 202122232425262728292a2b2c2d2e2f 303132333435363738393a3b3c3d3e3f
iv	00
input	000102030405060708090a0b0c0d0e0f 101112131415161718191a1b1c1d1e1f 202122232425262728292a2b2c2d2e2f 303132333435363738393a3b3c3d3e3f
expected	291724fb1390b08e56c19744ded6bf16 4bb1bb12020ea7ad13972545dd5c99b1 b48aadc1cd80429fc1e81e77d2f339b9 ba8b021a2736118ac6fb8c7a2f760efc

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