Package 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

  • Constructor Details

    • Crypt

      @Deprecated public Crypt()
      Deprecated.
      TODO Make private in 2.0.
      TODO Make private in 2.0.

  • Method Details

    • 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.

      A salt is generated for you using SecureRandom.

      Parameters:
      keyBytes - plaintext password
      Returns:
      hash value
      Throws:
      IllegalArgumentException - 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 - real salt value without prefix or "rounds=". The salt may be null, in which case a salt is generated for you using SecureRandom.
      Returns:
      hash value
      Throws:
      IllegalArgumentException - if the salt does not match the allowed pattern
      IllegalArgumentException - 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.

      A salt is generated for you using SecureRandom.

      Parameters:
      key - plaintext password
      Returns:
      hash value
      Throws:
      IllegalArgumentException - when a NoSuchAlgorithmException is caught.
      See Also:

    • 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 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 recognized 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 ($n$), where n is the same as the input salt. The salt is then appended, followed by a "$" sign. This is followed by the actual hash value. For DES the string only contains the salt and actual hash. The 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 - real salt value without prefix or "rounds=". The salt may be null, in which case a salt is generated for you using SecureRandom
      Returns:
      hash value, i.e. encrypted password including the salt string
      Throws:
      IllegalArgumentException - if the salt does not match the allowed pattern
      IllegalArgumentException - when a NoSuchAlgorithmException is caught. *
      See Also:
      • "The man page of the libc crypt (3) function."