MeridianMERIDIAN

Cryptographic Hash

technology.cryptographic.hash

Output of a cryptographic hash function (MD5, SHA-1, SHA-256, etc.). Detected as hex string of fixed length. Broad categorization by length.

Worked samples

DuckDB 1.5.5 · finetype 0.6.64

ValueAs VARCHARalgorithm
5d41402abc4b2a76b9719d911017c5925d41402abc4b2a76b9719d911017c592MD5
aaf4c61ddcc5e8a2dabede0f3b482cd9aea9434daaf4c61ddcc5e8a2dabede0f3b482cd9aea9434dSHA1
2c26b46911185131006dfb3b57a99d732c26b46911185131006dfb3b57a99d73MD5

Shape

Pattern
^[0-9a-f]{32}$|^[0-9a-f]{40}$|^[0-9a-f]{64}$|^[0-9a-f]{128}$
ValueLengthShape
5d41402abc4b2a76b9719d911017c59232matches
aaf4c61ddcc5e8a2dabede0f3b482cd9aea9434d40matches
2c26b46911185131006dfb3b57a99d7332matches
5d41402abc4b2a76b9719d911017c5931rejected: one character short

Told apart

1 of the 2 other cryptographic types accept every one of these samples on shape alone.

Background

Origin

RFC 1321, The MD5 Message-Digest Algorithm, was written by R. Rivest and published in April 1992.[1] RFC 1321 describes MD5 as producing a 128-bit fingerprint or message digest of its input.[1] RFC 1321 says the MD5 algorithm is intended for digital signature applications.[1] The reference code in RFC 1321 prints a message digest in hexadecimal.[1] The test suite in RFC 1321 gives the MD5 digest of the empty string as d41d8cd98f00b204e9800998ecf8427e.[1] MD5 hashes are typically represented as a sequence of 32 hexadecimal digits.[2]

SHA-1 produces a 160-bit (20-byte) hash value, typically written as 40 hexadecimal digits.[3] The SHA-2 family was designed by the National Security Agency and first published in 2001.[4] NIST's FIPS 180-4, the Secure Hash Standard, specifies seven hash algorithms: SHA-1, SHA-224, SHA-256, SHA-384, SHA-512, SHA-512/224 and SHA-512/256.[5] FIPS 180-4 states that the digests are used to detect whether messages have been changed since the digests were generated.[6]

Use

PostgreSQL's md5 function computes the MD5 hash of its argument with the result written in hexadecimal, so md5('abc') returns 900150983cd24fb0d6963f7d28e17f72.[7] Python's hashlib hexdigest method returns the digest as a string of double length containing only hexadecimal digits, for exchanging the value safely in email or other non-binary environments.[8]

NIST deprecated the use of SHA-1 in 2011 and disallowed its use for digital signatures at the end of 2013.[5] Researchers at CWI Amsterdam and Google published two different PDF files with the same SHA-1 hash on 23 February 2017.[3] The GNU Coreutils manual says the chance of two files accidentally having identical MD5 sums is vanishingly small, but that md5sum should not be considered secure against malicious tampering.[9] An MD5 or SHA-1 column is still fine for spotting duplicate or corrupted files, but treat it as weak evidence that nobody has tampered with them. (Meridian's view)

Where you'll meet it

The SHA256SUMS file for Debian's current amd64 CD images lists one 64-character lowercase hexadecimal digest per line, followed by the image's file name.[10]

Sources

  1. [1]RFC 1321: The MD5 Message-Digest Algorithmstandard
  2. [2]MD5secondary source
  3. [3]SHA-1secondary source
  4. [4]SHA-2secondary source
  5. [5]Hash Functions | CSRCorganisation
  6. [6]FIPS 180-4, Secure Hash Standard (SHS) | CSRCcatalogue entry
  7. [7]PostgreSQL: Documentation: 18: 9.4. String Functions and Operatorsdocumentation
  8. [8]hashlib — Secure hashes and message digestsdocumentation
  9. [9]md5sum invocation (GNU Coreutils 9.12)documentation
  10. [10]SHA256SUMSdataset

Detection notes

v1 migration: Was cryptographic.hash. Decompose infers algorithm from length: 32→MD5, 40→SHA1, 64→SHA256, 128→SHA512. No cryptographic validation (can't verify true hash without known input).

Use it

CLI · DuckDB
$ finetype infer -i "5d41402abc4b2a76b9719d911017c592" --mode column
→ technology.cryptographic.hash

SELECT ft_infer('5d41402abc4b2a76b9719d911017c592');
-- → 'technology.cryptographic.hash'
Cast expression
CAST({col} AS VARCHAR)

Schema

https://meridian.online/schemas/technology.cryptographic.hash · Frictionless type string

finetype taxonomy technology.cryptographic.hash -o json-schema

Type Registry