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ISAAC

ISAAC (Indirection, Shift, Accumulate, Add, Count) is a cryptographically secure PRNG designed by Bob Jenkins. Features 8KB internal state, extremely long period (minimum 2^40, average 2^8295), and high performance.

Properties

Property	Value
Category	Random Number Generators
Sub-category	Cryptographic PRNG
Security status	🧪 Experimental
Complexity	Intermediate
Inventor	Bob Jenkins
Year	1996
Origin	🇺🇸 United States
Source	algorithms/random/isaac.js

Parameters

Parameter	Supported values
Seed sizes	0 bytes (0 bits) to 1024 bytes (8192 bits)

Capabilities

Flag	Value
IsDeterministic	Yes
IsCryptographicallySecure	Yes

Security

Status: 🧪 Experimental

No vulnerabilities are recorded for this implementation.

Documentation

• ISAAC Homepage - Bob Jenkins
• ISAAC Paper - Fast Software Encryption 1996
• BouncyCastle Reference Implementation

References

• Wikipedia: ISAAC (cipher)
• Bob Jenkins’ Random Number Page

Test vectors

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

Vector 1 — BouncyCastle Test Vector #1 - Key: 00000000 (4 bytes)

Field	Value
seed	00000000
outputSize	2048
input	null
expected	f650e4c8e448e96d98db2fb4f5fad54f 433f1afbedec154ad837048746ca4f9a 5de3743e88381097f1d444eb823cedb6 6a83e1e04a5f6355c744243325890e2e … (2048 bytes; the full value is in the source)

Vector 2 — BouncyCastle Test Vector #2 - Key: FFFFFFFF (4 bytes)

Field	Value
seed	ffffffff
outputSize	288
input	null
expected	de3b3f3c19e0629c1fc8b7836695d523 e7804edd86ff7ce9b106f52caebae9d9 72f845d49ce17d7da44e49bae954aac0 d0b1284b98a88eec1524fb6bc91a16b5 … (288 bytes; the full value is in the source)

Vector 3 — BouncyCastle Test Vector #3 - Key: FFFF0000 pattern (1024 bytes)

Field	Value
seed	ffff0000ffff0000ffff0000ffff0000 ffff0000ffff0000ffff0000ffff0000 ffff0000ffff0000ffff0000ffff0000 ffff0000ffff0000ffff0000ffff0000 … (1024 bytes; the full value is in the source)
outputSize	576
input	null
expected	26c54b1f8c4e3fc582e9e8180f7aba53 80463dcf58b03cbeda0ecc8ba90ccff8 5bd50896313d7efed44015faeac6964b 241a7fb8a2e37127a7cbea0fd7c020f2 … (576 bytes; the full value is in the source)

Vector 4 — BouncyCastle Test Vector #4 - Key: 0000FFFF pattern (1024 bytes)

Field	Value
seed	0000ffff0000ffff0000ffff0000ffff 0000ffff0000ffff0000ffff0000ffff 0000ffff0000ffff0000ffff0000ffff 0000ffff0000ffff0000ffff0000ffff … (1024 bytes; the full value is in the source)
outputSize	576
input	null
expected	bc31712f2a2f467a5abc737c57ce0f8d 49d2f775eb850fc8f856daf19310fee2 5bab40e78403c9ef4ccd971418992faf 4e85ca643fa6b482f30c4659066158a6 … (576 bytes; the full value is in the source)

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