Crate json_digest

This library provides some algorithms to calculate cryptographically secure digests of JSON documents. Since JSON is an ambiguous serialization format, we also had to define a canonical deterministic subset of all allowed documents. Order of keys in an object and Unicode normalization are well-defined in this subset, making it suitable for hashing.

let data = serde_json::json!({
  "address": {
    "value": "6 Unter den Linden, Berlin, Germany",
    "nonce": "uN_FTaYe8JM-EZ8SU94kAOf0k0YvnhLcZgdpQ3BU9Ymbu"
  },
  "dateOfBirth": {
    "value": "16/02/2002",
    "nonce": "ufxkENKgXuf4yG50p6xpSyaQ8Gz7KsuqXid2yw533TUMK"
  },
  "placeOfBirth": {
    "city": "Berlin",
    "country": "Germany",
    "nonce": "ukhFsI4a6vIZEDUOBRxJmLroPEQ8FQCjJwbI-Z7bEocGo"
  },
});

let digest = json_digest::digest_data(&data).unwrap();
assert_eq!(digest, "cjuQR3pDJeaiRv9oCZ-fBE7T8QWpUGfjP40sAXq0bLwr-8");

let partial_digest = json_digest::selective_digest_data(&data, ".dateOfBirth").unwrap();
let expected_partial_digest = serde_json::json!({
  "address": "cjuvIf1PmPH_31JN5XqJ1xkcNDJyiw9zQ-7ansSB78gnt4",
  "dateOfBirth": {
    "nonce": "ufxkENKgXuf4yG50p6xpSyaQ8Gz7KsuqXid2yw533TUMK",
    "value":"16/02/2002"
  },
  "placeOfBirth": "cjub0Nxb0Kz0pI4bWCdSbaCutk1s5qieFT-ZmqUU1xcuAc"
});
assert_eq!(partial_digest, serde_json::to_string(&expected_partial_digest).unwrap());

let digest_from_partial = json_digest::digest_json_str(&partial_digest).unwrap();
assert_eq!(digest, digest_from_partial);

Modules

json_path

Utility functions to specify subtrees in a JSON document. Path pattern syntax is based on JQ patterns, see https://stedolan.github.io/jq/manual/#Basicfilters

Structs

Nonce264

Multibase-encoded random content, e.g. “urvU8F6HmEol5zOmHh_nnS1RiX5r3T2t9U_d_kQY7ZC-I”

Functions

canonical_json

Constructs the deterministic string representation of the provided JSON value.

default_hasher

Multibase-encoded hash of the provided bytes used in many places around this crate.

digest_data

Convenience function for serializable types to mask the whole JSON tree into a digest, keep nothing.

digest_json_str

Convenience function for JSON strings to mask the whole JSON tree into a digest, keep nothing.

mask_json_subtree

Replace JSON (sub)tree(s) with their multibase-encoded Merkle-root hash strings.

normalize_unicode

Returns an NFKD normalized unicode representation of the input

selective_digest_data

Convenience function calling selective_digest_json with arbitrary serializable types.

selective_digest_json

Convenience function to transform a JSON value into a (partially) masked JSON value. Only subtrees matching the provided JSON path pattern will be kept, all other subtrees will be masked.

selective_digest_json_str

Convenience function calling selective_digest_json with a JSON string.