LFSR-based stream cipher using irregular decimation by Coppersmith, Krawczyk, and Mansour. Uses two LFSRs where one controls bit selection from the other.
| Property | Value |
|---|---|
| Category | Stream Ciphers |
| Sub-category | Stream Cipher |
| Security status | 🎓 Educational Only |
| Complexity | Intermediate |
| Inventor | Don Coppersmith, Hugo Krawczyk, Yishay Mansour |
| Year | 1993 |
| Origin | 🇺🇸 United States |
| Source | algorithms/stream/shrinking-generator.js |
| Parameter | Supported values |
|---|---|
| Key sizes | 16 bytes (128 bits) |
Status: 🎓 Educational Only
| Issue | Description | Mitigation |
|---|---|---|
| Variable Output Rate | Output rate varies irregularly which can leak information about internal state | Use output buffering to mask timing variations |
| Known Polynomial Attack | If LFSR feedback polynomials are known, attacks require less than A*S bits of output | Keep feedback polynomials secret and use strong polynomial selection |
3 vectors ship with this algorithm and run in the test suite. Byte values are hexadecimal.
Vector 1 — Shrinking Generator - Zero key test vector
Source: Generated from CRYPTO ‘93 algorithm specification
| Field | Value |
|---|---|
key |
00000000000000000000000000000001 |
input |
00000000000000000000000000000000 |
expected |
0023f77c58e03cf399e9e63b6981cb3b |
Vector 2 — Shrinking Generator - Pattern key test vector
Source: Generated from CRYPTO ‘93 algorithm specification
| Field | Value |
|---|---|
key |
0123456789abcdef0123456789abcdef |
input |
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa |
expected |
fdfd69daf7ac95f9ef7c03500d464010 |
Vector 3 — Shrinking Generator - Full key test vector
Source: Generated from CRYPTO ‘93 algorithm specification
| Field | Value |
|---|---|
key |
fedcba9876543210fedcba9876543210 |
input |
ffffffffffffffffffffffffffffffff |
expected |
49839f0a11c8cb4613becb4e92c6c6d1 |