Verifying the authenticity of a file by its hash

  1. Start the Python shell and configure its session.

    The following variables should be available now:

    >>> base_url  # the base URL of the API
    >>> auth  # the 'Authorization' header value with the access token
    {'Authorization': 'Bearer 8770b34b74f9e4d9424eff50c38182bb4ae7f5596582ae61900b1b6a23e3ec58'}
  2. Define a variable named file_path, and then assign the path to your file to this variable:

    >>> file_path = '<path to file>'


    If the path contains backslashes, remember to escape them with an additional backslash.

  3. Define a variable named certificate_id, and then assign the ID of the certificate that is corresponding to this hash to this variable:

    >>> certificate_id = '7605f73deaee7b071a570b3ac20cc9fe7a3abf337be7c86c55c28af9d3d8435c'
  4. Open the file for reading in binary mode:

    >>> file = open(file_path, 'rb')
  5. Calculate the hash value of the file contents by using the SHA-256 algorithm:

    >>> sha256 = hashlib.sha256()
    >>> chunk = * sha256.block_size)
    >>> while chunk:
    ...     sha256.update(chunk)
    ...     chunk = * sha256.block_size)
    >>> file_hash = sha256.hexdigest()
    >>> file_hash
  6. Close the file:

    >>> file.close()
  7. Define a variable named hash_data, and then assign an object with the following JSON parameters to this variable:

    >>> hash_data = {
    ...     'hash': file_hash,
    ...     'certificate_hash': certificate_id
    ... }
  8. Convert the hash_data object to a JSON text:

    >>> hash_data = json.dumps(hash_data, indent=4)
  9. Send a POST request with the JSON text to the /hashes/verify endpoint:

    >>> response =
    ...     f'{base_url}/hashes/verify',
    ...     headers={'Content-Type': 'application/json', **auth},
    ...     data=hash_data,
    ... )


    The /hashes/verify endpoint does not require authentication so Authorization header can be safely omitted.

  10. Check the status code of the response:

    >>> response.status_code

    Status code 200 means that the notary service has found notarization certificates for this file (the file is notarized or is being notarized) and responded to you with this data. If the status code is 404, no certificates are found (the service has never received and notarized the file).

    A different status code means that an error has occurred. For the details, refer to “Status and error codes”.

    Also, the response body contains the certificates key containing an array of notarization certificate objects formatted as a JSON text. When converted to an object, it will look as follows:

    >>> pprint.pprint(response.json())
    {'certificates': [{'contract': '0xd10e3Be2bc8f959Bc8C41CF65F60dE721cF89ADF',
                       'eventtime': '2019-11-11T13:07:07.004366Z',
                       'id': '7605f73deaee7b071a570b3ac20cc9fe7a3abf337be7c86c55c28af9d3d8435c',
                       'merkle_proof': '[{"left":"88c20ca21dd6fa9e0a64c7e981a012812bbca152010195cd4296d959cfa35f1e"}]',
                       'merkle_root': '6d05fb9f0c2cff4942987661a44e71f0f554d435ce494dd3e7a21df6c6ba963c',
                       'notarized_location': 'beta-baas',
                       'object': {'eTag': '2c7c3d5f244f1a40069a32224215e0cf9b42485c99d80f357d76f006359c7a18',
                                  'key': '2c7c3d5f244f1a40069a32224215e0cf9b42485c99d80f357d76f006359c7a18',
                                  'sequencer': '89a8927268f22ee9af',
                                  'size': 0},
                       'blockchain': 'eth',
                       'qr_code': 'data:image/png;base64,iVBORw0KGgoAAAANSUh...',
                       'sender': '0x201354729f8d0f8b64e9a0c353c672c6a66b3857',
                       'signee_details': {'tenant_name': 'John Doe'},
                       'timestamp': 1573572432,
                       'txid': '0x6494a098f6487ebbcfa85b7cbe64c1f9f077f03866477b67be64320ea109fa73',
                       'version': '3.1'}]}

    If the notarization is complete:

    • The txid key contains the hash of the blockchain transaction that can be viewed on{txid}.

    • The contract, sender, merkle_root, and merkle_proof keys contain the blockchain transaction details.

    • The timestamp key contains the Unix time when the hash value of the file contents was written to the blockchain (notarization completion time).

    • The eTag key of the object object contains the actual hash value that was written to the blockchain.

    • The web version of the notarization certificate is available at{certificate_id}.

    Empty txid, contract, merkle_proof, merkle_root, and sender keys mean that the notarization is still in progress and the web version of the certificate is not created yet.

Full code example

 1#!/usr/bin/env python3
 3import requests  # Will be used for sending requests to the API.
 4import hashlib   # Will be used for calculating hash values.
 5import os.path   # Will be used for path-related operations.
 6import pprint    # Will be used for formatting the output of JSON objects received in API responses.
 7import json      # Will be used for converting dictionaries into JSON text
 9# Define variables named "LOGIN" and "PASSWORD" and then assign them with your account credentials
10LOGIN = '<your login>'        # Change login here
11PASSWORD = '<your password>'  # Change password here
13# Define a variable named "cloud_url" and then assign it with the URL of the cloud platform
14cloud_url = ''
16# Fetch the URL of the data center where your account is located by sending a GET request to the "/api/1/accounts" endpoint
17response = requests.get(
18    f'{cloud_url}/api/1/accounts',
19    params={'login': LOGIN}
23# Convert the JSON text that the response body contains to a dictionary and store the data center URL
24# in a variable that will be used in further requests
25server_url = response.json()['server_url']
27# Define a variable named "account_creds", and then assign the username and password to this variable
28account_creds = {
29    'username': LOGIN,
30    'password': PASSWORD
33# Generate a token by sending a POST request to the "/api/2/idp/token" with your account credentials to the cloud platform
34response =
35    f'{server_url}/api/2/idp/token',
36    headers={'Content-Type': 'application/x-www-form-urlencoded'},
37    data={'grant_type': 'password', **account_creds}
41# Convert the JSON text that the response body contains to a dictionary and then assign it to a variable named "token_info"
42token_info = response.json()
44# Define a variable named "auth" and then assign it with a dictionary with "Authorization" key containing
45# token string formatted as "Bearer <access_token>"
46auth = {
47    'Authorization': 'Bearer ' + token_info['access_token']
50# Define a variable named "base_url", and then assign the API base URL using the data center URL
51# to this variable
52base_url = f'{server_url}/api/notary/v2'
54# Define a variable named "file_id" and then assign it with the ID of the file
55file_path = '<path to file>'  # Change path to file here
57# Define a variable named "certificate_id" and then assign it with the ID of the certificate that is corresponding to this file
58certificate_id = '7605f73deaee7b071a570b3ac20cc9fe7a3abf337be7c86c55c28af9d3d8435c'
60# Open the file for reading in binary mode
61file = open(file_path, 'rb')
63# Calculate the SHA-256 hash of the file
64sha256 = hashlib.sha256()
65chunk = * sha256.block_size)
66while chunk:
67    sha256.update(chunk)
68    chunk = * sha256.block_size)
69file_hash = sha256.hexdigest()
71# Close the file
74hash_data = {
75    'hash': file_hash,
76    'certificate_hash': certificate_id
79# Convert the "hash_data" dictionary to a JSON text
80hash_data = json.dumps(hash_data, indent=4)
82# Send the file hash for verification by sending a POST request to the "/hashes/verify" endpoint
83response =
84    f'{base_url}/hashes/verify',
85    headers={'Content-Type': 'application/json', **auth},
86    data=hash_data,