org.apache.commons.codec.digest

## Class Crypt

- java.lang.Object
- - org.apache.commons.codec.digest.Crypt

-     public class Crypt
      extends Object

  GNU libc crypt(3) compatible hash method.

  See `crypt(String, String)` for further details.

  This class is immutable and thread-safe.

  Since:
    1.7
  Version:
    $Id: Crypt.java 1429868 2013-01-07 16:08:05Z ggregory $

- - ### Constructor Summary

    Constructors
    Constructor and Description
    `Crypt()`

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `static String` | `crypt(byte[] keyBytes)` Encrypts a password in a crypt(3) compatible way.
    `static String` | `crypt(byte[] keyBytes, String salt)` Encrypts a password in a crypt(3) compatible way.
    `static String` | `crypt(String key)` Calculates the digest using the strongest crypt(3) algorithm.
    `static String` | `crypt(String key, String salt)` Encrypts a password in a crypt(3) compatible way.

    - ### Methods inherited from class java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

- - ### Constructor Detail

    - #### Crypt

          public Crypt()

  - ### Method Detail

    - #### crypt

          public static String crypt(byte[] keyBytes)

      Encrypts a password in a crypt(3) compatible way.

      A random salt and the default algorithm (currently SHA-512) are used. See `crypt(String, String)` for details.

      Parameters:
        `keyBytes` - plaintext password
      Returns:
        hash value
      Throws:
        `RuntimeException` - when a `NoSuchAlgorithmException` is caught.

    - #### crypt

          public static String crypt(byte[] keyBytes,
                     String salt)

      Encrypts a password in a crypt(3) compatible way.

      If no salt is provided, a random salt and the default algorithm (currently SHA-512) will be used. See `crypt(String, String)` for details.

      Parameters:
        `keyBytes` - plaintext password
        `salt` - salt value
      Returns:
        hash value
      Throws:
        `IllegalArgumentException` - if the salt does not match the allowed pattern
        `RuntimeException` - when a `NoSuchAlgorithmException` is caught.

    - #### crypt

          public static String crypt(String key)

      Calculates the digest using the strongest crypt(3) algorithm.

      A random salt and the default algorithm (currently SHA-512) are used.

      Parameters:
        `key` - plaintext password
      Returns:
        hash value
      Throws:
        `RuntimeException` - when a `NoSuchAlgorithmException` is caught.
      See Also:
        `crypt(String, String)`

    - #### crypt

          public static String crypt(String key,
                     String salt)

      Encrypts a password in a crypt(3) compatible way.

      The exact algorithm depends on the format of the salt string:

      - SHA-512 salts start with $6$ and are up to 16 chars long.
      - SHA-256 salts start with $5$ and are up to 16 chars long
      - MD5 salts start with "$1$" and are up to 8 chars long
      - DES, the traditional UnixCrypt algorithm is used else with only 2 chars
      - Only the first 8 chars of the passwords are used in the DES algorithm!
      The magic strings "$apr1$" and "$2a$" are not recognised by this method as its output should be identical with that of the libc implementation.

      The rest of the salt string is drawn from the set [a-zA-Z0-9./] and is cut at the maximum length of if a "$" sign is encountered. It is therefore valid to enter a complete hash value as salt to e.g. verify a password with:

           storedPwd.equals(crypt(enteredPwd, storedPwd))

      The resulting string starts with the marker string ($6$), continues with the salt value and ends with a "$" sign followed by the actual hash value. For DES the string only contains the salt and actual hash. It's total length is dependent on the algorithm used:

      - SHA-512: 106 chars
      - SHA-256: 63 chars
      - MD5: 34 chars
      - DES: 13 chars

      Example:

                crypt("secret", "$1$xxxx") => "$1$xxxx$aMkevjfEIpa35Bh3G4bAc."
                crypt("secret", "xx") => "xxWAum7tHdIUw"

      This method comes in a variation that accepts a byte[] array to support input strings that are not encoded in UTF-8 but e.g. in ISO-8859-1 where equal characters result in different byte values.

      Parameters:
        `key` - plaintext password as entered by the used
        `salt` - salt value
      Returns:
        hash value, i.e. encrypted password including the salt string
      Throws:
        `IllegalArgumentException` - if the salt does not match the allowed pattern
        `RuntimeException` - when a `NoSuchAlgorithmException` is caught. *
      See Also:
        "The man page of the libc crypt (3) function."

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