Credentials API

The Credentials API allows you to securely lookup whether a given username/password combination exists in our database of compromised account credentials. The typical example where this API can be useful is on your website’s or company’s login form. As users login, you can check their credentials against this API to ensure that they have not been compromised. In the event that a user’s credentials have been exposed, you can force them to reset their password. In this way, you can prevent criminals from logging in using stolen credentials and ensure that they are changed by the legitimate user the very next time they login.

Available Calls

  • GET Credentials (Hash-based)
    Check whether a given set of user credentials are known to be compromised. Credentials are passed in as secure partial hashes.

GET Credentials (Hash-Based)

The Hash-Based Credentials API allows you to securely query the Enzoic credentials database without passing the raw credentials.


Using the Hash-Based Credentials API is a multi step process, as follows:

  1. Retrieve the Account Salt and Hashes
    Make a GET call to the /accounts API endpoint with desired username or a SHA256 hash of the username. This will return a salt value, as well as an array of PasswordHashSpecifications containing hash types (algorithms and potentially salts). If this call returns a 404, it indicates that we have no compromised credentials for this username and you can skip the remaining steps.
  2. Calculate Requested Password Hashes
    For each entry in the returned hashes array, construct a hash of the user’s password using the specified hashing algorithm and salt value. See the table of hash algorithms here for reference:hash types
  3. Calculate Credential Hashes
    For each resultant password hash from step 2, construct a credentials hash by concatenating the username and password together, and then calculating an Argon2 hash of the result using the Account salt returned in step 1.
  4. Make Credentials API Call
    Make a GET call to the /credentials API endpoint with the array of Argon2 hashes from step 3. The result will indicate whether the credentials have been compromised.

More detail for each step follows below.

Step 1 – Retrieve the Account Salt and Hashes

The first step is to make a GET call to the /accounts API endpoint to retrieve the account-specific salt value and a list of required hashes. The /accounts call is as follows:

GET<username or hash>
Parameter Type Description
username string The username/email or SHA-256 hash of the lowercase username/email of the user
Response Description
200 The username was found in the Enzoic database and the response contains the user-specific salt value and an array of password hashes which must be calculated for a subsequent Credentials API call.
404 The username was not found in the Enzoic database and has no compromised credentials associated with it. No further action is necessary.
Response Body
Member Type Description
salt string The salt value to use when constructing the Argon2 Credentials Hashes
passwordHashesRequired PasswordHashSpecification[] An array of password hash specifications.
lastBreachDate string A string containing the date/time of the last credentials exposure found for this account. This can be used to more intelligently check credentials for a user, i.e. if the lastBreachDate is less than the last time you performed a credentials check, you can skip the remaining steps.

Member Type Description
hashType PasswordHashType The hash algorithm to use (see PasswordHashType enum). The password should be in UTF-8 encoding prior to hashing.
salt string The salt value to use with the algorithm, if applicable. If an empty string, no salt value should be used.


Value Description Output
1 MD5 hash algorithm without salt Hex string
2 SHA1 hash algorithm without salt Hex string
3 SHA256 hash algorithm without salt Hex string
5 Composite Algorithm: md5(md5(salt) + md5(password)) Hex string
6 Composite Algorithm: md5(md5(password) + salt) Hex string
7 Composite Algorithm: md5(md5(password) + salt) Hex string
8 BCrypt algorithm using provided salt Bcrypt string
9 CRC32 hash algorithm without salt Hex string
10 PHPBB3 (PHPass) PHPass string
11 Composite Algorithm: xor(sha512(password + salt), whirlpool(salt + password)) Hex string
13 Composite Algorithm: md5(password + salt) Hex string
14 SHA512 hash algorithm without salt Hex string
15 Composite Algorithm with fixed salt: md5(“kikugalanet” + password) Hex string
16 MD5Crypt algorithm using provided salt MD5Crypt string
17 Composite Algorithm: bcrypt(md5(password)) using provided salt for BCrypt BCrypt string
18 Composite Algorithm: sha256(md5(password + salt)) Hex string
19 Composite Algorithm: md5(salt + password) Hex string
20 DESCrypt algorithm using provided salt DESCrypt string
21 MySQL (pre 4.1) algorithm Hex string
22 Composite Algorithm: “*” + sha1(sha1(password)) Hex string prefixed with “*”
23 Composite Algorithm: base64(sha1(UTF16Bytes(password))) Hex string
24 Composite Algorithm: sha1(salt + sha1(password)) Hex string
25 Composite Algorithm: sha1(password + salt) Hex string
26 Partial MD5 – first 20 bytes of MD5 hash of password Hex string
27 Composite Algorithm: md5(md5(password)) Hex string
28 Composite Algorithm: “md5$” + salt + “$” + md5(salt + password) Hex string
29 Composite Algorithm: “sha1$” + salt + “$” + sha1(salt + password) Formatted hex string
30 Partial MD5 – first 29 bytes of MD5 hash of password Hex string
31 Composite Algorithm: salt + sha1(salt + password) Formatted hex string
32 Composite Algorithm: sha1(username + password) Hex string
33 NTLM Hex string
34 Composite Algorithm: sha1(“–” + salt + “–” + password + “–“) Hex string
35 SHA384 Hex string
36 Composite Algorithm: hmac-sha256(sha1(salt) + password)
HMAC key: “d2e1a4c569e7018cc142e9cce755a964bd9b193d2d31f02d80bb589c959afd7e”
Hex string
37 Composite Algorithm: sha256(salt + password) Hex string
38 Composite Algorithm: sha512<11 times>(sha512(password + salt)) Hex string
39 SHA512Crypt SHA512Crypt string
40 Composite Algorithm: sha512(password + “:” + salt) Hex string


curl -v --header "authorization: basic {your auth string}" ""
  "salt": "aa101973b4ea4ad698b42d20303a9527",
  "passwordHashesRequired": [
          "hashType": 1,
          "salt": ""
          "hashType": 2,
          "salt": ""
  "lastBreachDate": "2016-12-10T02:05:03.000Z"

Step 2 – Calculate the Requested Password Hashes

Next, iterate over the passwordHashesRequired array returned in step 1, calculating a password hash as specified by the hashType of each PasswordHashSpecification entry.


Some of the hashTypes are standard hashing algorithms, such as SHA-1 and BCrypt, while others are composite algorithms, combining the password, salt, and potentially multiple standard hashes together to calculate a final hash value. For example, hashType 5 is a composite with the following algorithm: md5(md5(salt) + md5(password)). Thus, it would be necessary to calculate an MD5 of the provided salt and concatenate this with an MD5 of the password. Finally, an MD5 of the resultant string is calculated and this is the final hash. Unless otherwise specified, the standard hash steps in a composite algorithm should all be outputting lowercase hex string representations of the value.


Note that some of the hashTypes require salt values and some do not, depending on the hash algorithm. When the salt value is not required for the specified algorithm, it will be an empty string.

Hash Libraries

Calculating these hashes will involve language-specific libraries to provide standard hashing functions (MD5, SHA-1, SHA-256, etc). Typically these functions are either built-in or available as open-source libraries for practically any widely-used programming language.

Step 3 – Calculate the Credential Hashes

For each item in the password hashes array produced in step 2, concatenate the username and password hash and then hash the result with the Argon2 algorithm and the account salt returned in step 1. Lastly, extract just the hash value from the Argon2 hash (the string will also contain the algorithm hash parameters and salt value used). This should result in an array of Credential Hashes, which will be the arguments passed to the Credentials API in the final step.


for (var i = 0; i < passwordHashes.length; i++) { 
  // concatenate the username, "$", and password hash value from step 2 into a single string
  var toHash = username + "$" + passwordHashes[i];
  // calculate the Argon2 hash (Argon2 library for your programming language required)
  var argon2Hash = Argon2(toHash, accountSalt);
  // extract just the hash value from the resultant Argon2 string (should be everything after the last "$"
  credentialHashes[i] = argon2Hash.substr(argon2Hash.lastIndexOf("$") + 1);

When calculating the Credential Hash, the Argon2 algorithm should be called with the following settings:

Setting Value
Type Argon2d
Iterations/TimeCost 3
Memory 1024
Parallelism 2
HashLength 20

Step 4 – Make the Credentials API Call

The final step is to make a GET call to the /credentials API endpoint, passing in a list of the first 10 hex characters from each Credential Hash calculated in step 3. Note that many Argon2 libraries will return a hash result in Base64, so it may be necessary to convert the hash into a hex string before extracting the first 10 characters. The /credentials call in this case is as follows:

Parameter Type Description
partialHashes string[] A list of the first 10 hex characters of Argon2 Credential Hashes
Response Description
200 One or more candidate credentials matches were found in Enzoic’s database of compromised credentials. The candidate hashes are returned in the response body. You should compare the full hash(es) to the list of returned candidates. If a match is found, the credentials are compromised.
404 The credentials were not found in Enzoic’s database and have not been compromised.
Response Body

The response body contains an array of candidate credential hashes which match one or more of the hash prefixes provided. Each candidate entry should be compared against the full Credential Hashes you calculated in step 3. If a match exists, the credentials are compromised.

Member Type Description
candidateHashes string[] A list of credential hashes from the Enzoic database that match the first 10 characters of the hash(es) which were passed in


curl -v --header "authorization: basic {your auth string}" ""
  "candidateHashes": [

Test Accounts

Test accounts are available for all of the hash types above. Test accounts all have the same form:

Username: eicar_(passwordType)
Password: 123456

So, for example, to test an account with a BCrypt password in the Enzoic database, you would use a username of: