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SYSV-Checksum

Unix System V checksum algorithm used by the ‘sum’ command. Simple sum of all bytes with modulo 32-bit arithmetic. Historical Unix utility for basic file integrity verification. Compatible with System V sum -s option.

Properties

Property	Value
Category	Checksums
Sub-category	Unix Utility
Security status	🎓 Educational Only
Complexity	Beginner
Inventor	AT&T Bell Labs
Year	1983
Origin	🇺🇸 United States
Source	algorithms/checksum/sysv-checksum.js

Security

Status: 🎓 Educational Only

No vulnerabilities are recorded for this implementation.

Notes

• Algorithm: Sum all bytes, result mod 2^16
• Output: 16-bit checksum (0-65535)
• Used in: System V Unix ‘sum -s’ command
• Simple and fast but weak error detection
• Does not detect reordering of blocks
• Superseded by stronger checksums (CRC, MD5, SHA)
• Historical significance in Unix systems

Documentation

• sum Command Manual
• Unix Checksum Algorithms
• System V Documentation

References

• GNU coreutils sum.c (sysv_sum_file) reference implementation

Test vectors

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

Vector 1 — Simple ASCII

Source: SYSV checksum

Field	Value
input	68656c6c6f
expected	0214

Vector 2 — Single byte

Source: SYSV checksum

Field	Value
input	42
expected	0042

Vector 3 — Multiple bytes

Source: SYSV checksum

Field	Value
input	01020304
expected	000a

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