json-fingerprint 0.9.2

Create consistent and comparable fingerprints with secure hashes from unordered JSON data

json-fingerprint

Create consistent and comparable fingerprints with secure hashes from unordered JSON data.

A json fingerprint consists of three parts: the version of the underlying algorithm, the hash function used and a hex digest of the hash function output. A complete example could look like this: jfpv1$sha256$5815eb0ce6f4e5ab0a771cce2a8c5432f64222f8fd84b4cc2d38e4621fae86af.

The first part indicates the algorithm version, jfpv1, which would translate to json fingerprint version 1. The second part, sha256, indicates that SHA256 is the hash function that was used. The last part, 5815eb0ce6f4e5ab0a771cce2a8c5432f64222f8fd84b4cc2d38e4621fae86af, is a standard hex digest of the hash function output.

Table of Contents

• v1 release checklist (jfpv1)
• Installation
• Examples
  • Creating fingerprints from JSON data
  • Decoding JSON fingerprints
  • Fingerprint matching

v1 release checklist (jfpv1)

This is a list of high-level development and documentation tasks, which need to be completed prior to freezing the API for v1. Prior to v1, backwards-incompatible changes are possible.

• Formalized the jfpv1 specification
• JSON type support
  • Primitives and literals
  • Arrays
  • Objects
• Flattened "sibling-aware" internal data structure
• Support nested JSON data structures with mixed types
• Support most common SHA-2 hash functions
  • SHA256
  • SHA384
  • SHA512
• Dynamic jfpv1 fingerprint comparison function (JSON string against a fingerprint)
• Performance characteristics that scale sufficiently
• Extensive verification against potential fingerprint (hash) collisions

Installation

To install the json-fingerprint package, run pip install json-fingerprint.

Examples

The complete working examples below show how to create and compare JSON fingerprints.

Creating fingerprints from JSON data

Fingerprints can be created with the json_fingerprint() function, which requires three arguments: input (valid JSON string), hash function (sha256, sha384 and sha512 are supported) and JSON fingerprint version (1).

import json

from json_fingerprint import json_fingerprint

obj_1_str = json.dumps([3, 2, 1, [True, False], {'foo': 'bar'}])
obj_2_str = json.dumps([2, {'foo': 'bar'}, 1, [False, True], 3])  # Same data in different order
fp_1 = json_fingerprint(input=obj_1_str, hash_function='sha256', version=1)
fp_2 = json_fingerprint(input=obj_2_str, hash_function='sha256', version=1)
print(f'Fingerprint 1: {fp_1}')
print(f'Fingerprint 2: {fp_2}')

This will output two identical fingerprints regardless of the different order of the json elements:

Fingerprint 1: jfpv1$sha256$164e2e93056b7a0e4ace25b3c9aed9cf061f9a23c48c3d88a655819ac452b83a
Fingerprint 2: jfpv1$sha256$164e2e93056b7a0e4ace25b3c9aed9cf061f9a23c48c3d88a655819ac452b83a

Since json objects with identical data content and structure will always produce identical fingerprints, the fingerprints can be used effectively for various purposes. These include finding duplicate json data from a larger dataset, json data cache validation/invalidation and data integrity checking.

Decoding JSON fingerprints

JSON fingerprints can be decoded with the decode_fingerprint() convenience function, which returns the version, hash function and hash in a tuple.

from json_fingerprint import decode_fingerprint

fingerprint = 'jfpv1$sha256$164e2e93056b7a0e4ace25b3c9aed9cf061f9a23c48c3d88a655819ac452b83a'
version, hash_function, hash = decode_fingerprint(fingerprint=fingerprint)
print(f'Version (integer): {version}')
print(f'Hash function: {hash_function}')
print(f'Hash: {hash}')

This will output the individual elements that make up a fingerprint as follows:

Version (integer): 1
Hash function: sha256
Hash: 164e2e93056b7a0e4ace25b3c9aed9cf061f9a23c48c3d88a655819ac452b83a

Fingerprint matching

The fingerprint_match() is another convenience function that matches JSON data against a fingerprint, and returns either True or False depending on whether the data matches the fingerprint or not. Internally, it will automatically choose the correct version and hash function based on the target_fingerprint argument.

import json

from json_fingerprint import fingerprint_match

input_1 = json.dumps([3, 2, 1, [True, False], {'foo': 'bar'}])
input_2 = json.dumps([3, 2, 1])
target_fingerprint = 'jfpv1$sha256$164e2e93056b7a0e4ace25b3c9aed9cf061f9a23c48c3d88a655819ac452b83a'
match_1 = fingerprint_match(input=input_1, target_fingerprint=target_fingerprint)
match_2 = fingerprint_match(input=input_2, target_fingerprint=target_fingerprint)
print(f'Fingerprint matches with input_1: {match_1}')
print(f'Fingerprint matches with input_2: {match_2}')

This will output the following:

Fingerprint matches with input_1: True
Fingerprint matches with input_2: False