SSH Key MD5-Style Fingerprint Formatter

Format a supplied 16-byte MD5 fingerprint as the lowercase colon-separated form used by SSH tooling.

Description

SSH tools can display a legacy MD5 key fingerprint as colon-separated hexadecimal byte pairs with an MD5 prefix.

SSH tools can display a legacy MD5 key fingerprint as colon-separated hexadecimal byte pairs with an MD5 prefix. Formatting a supplied digest is separate from hashing the actual public key or establishing its identity.^[1]

Format a supplied 16-byte MD5 fingerprint as the lowercase colon-separated form used by SSH tooling.

When to use SSH Key MD5-Style Fingerprint Formatter

Use this tool to format a supplied 16-byte MD5 fingerprint as the lowercase colon-separated form used by SSH tooling.

Choose the text, counts, explicit reference time or format parameters requested by this tool. Follow the stated byte, epoch-time and randomness assumptions.

How to use SSH Key MD5-Style Fingerprint Formatter and understand its results

Choose the text, counts, explicit reference time or format parameters requested by this tool. Follow the stated byte, epoch-time and randomness assumptions.
Enter hex using the field table and calculation rules, then run the tool.
Read fingerprint. The explanation below defines the units, signs, ordering and any flags or placeholder values.
If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.

Input field	Meaning	Value type; see rules below	Requirement
hex	MD5 fingerprint hexadecimal	string; maximum length: 32	Required

Enter exactly 32 hexadecimal characters representing a 16-byte digest, without separators or a prefix. The tool validates ASCII hex syntax, lowercases it, groups it into pairs and prefixes MD5:. The output contains sixteen pairs in their original byte order.

fingerprint = 'MD5:' + lowercase hex grouped into colon-separated pairs

Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.

Output field	Meaning	Value type
fingerprint	SSH-style MD5 fingerprint	string

json

{
  "input": {
    "hex": "00112233445566778899AABBCCDDEEFF"
  },
  "output": {
    "fingerprint": "MD5:00:11:22:33:44:55:66:77:88:99:aa:bb:cc:dd:ee:ff"
  }
}

Limitations and assumptions

This does not compute MD5, parse an SSH key or compare a fingerprint with a trusted record. It is a representation formatter rather than a recommendation of MD5 for security. Existing colons, whitespace and other digest lengths are rejected.

Numeric inputs must be finite. Follow the calculation-specific rules for overflow, underflow and exceptional cases. Extremely large text inputs are rejected. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors.

Alternative or Complementary methods

Use GPG Fingerprint Colon Formatter: Format a supplied v4 20-byte or v6 32-byte OpenPGP fingerprint as uppercase colon-separated hexadecimal byte pairs. For a complementary task, use Random Hex Token Bits From Characters: Return the ideal uniform-random capacity of a hexadecimal token from its number of independently random characters.

References

SSH Key MD5-Style Fingerprint Formatter — tool.io

Similar or alternative tools

GPG Fingerprint Colon Formatter
Format a supplied v4 20-byte or v6 32-byte OpenPGP fingerprint as uppercase colon-separated hexadecimal byte pairs.
Random Hex Token Bits From Characters
Return the ideal uniform-random capacity of a hexadecimal token from its number of independently random characters.