Package org.conscrypt

Class Hkdf

  • public final class Hkdf
extends java.lang.Object
    Hkdf - perform HKDF key derivation operations per RFC 5869.

    Instances should be instantiated using the standard JCA name for the required HMAC.

    Each invocation of expand or extract uses a new Mac instance and so instances of Hkdf are thread-safe.

    • Field Summary

      Fields 
      Modifier and Type Field Description
      private java.lang.String hmacName  
      private int macLength  

    • Constructor Summary

      Constructors 
      Constructor Description
      Hkdf​(java.lang.String hmacName)
      Creates an Hkdf instance which will use hmacName as the name for the underlying HMAC algorithm, which will be located using normal JCA precedence rules.

    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      byte[] expand​(byte[] prk, byte[] info, int length)
      Performs an HKDF expand operation as specified in RFC 5869.
      byte[] extract​(byte[] salt, byte[] ikm)
      Performs an HKDF extract operation as specified in RFC 5869.
      private javax.crypto.Mac getMac​(byte[] key)  
      int getMacLength()  

      • Methods inherited from class java.lang.Object

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

    • Field Detail

      • hmacName

        private final java.lang.String hmacName

      • macLength

        private final int macLength

    • Constructor Detail

      • Hkdf

        public Hkdf​(java.lang.String hmacName)
     throws java.security.NoSuchAlgorithmException
        Creates an Hkdf instance which will use hmacName as the name for the underlying HMAC algorithm, which will be located using normal JCA precedence rules.

        Parameters:
        hmacName - the name of the HMAC algorithm to use
        Throws:
        java.security.NoSuchAlgorithmException - if hmacName is not a valid HMAC name

    • Method Detail

      • getMacLength

        public int getMacLength()

      • extract

        public byte[] extract​(byte[] salt,
                      byte[] ikm)
               throws java.security.InvalidKeyException,
                      java.security.NoSuchAlgorithmException
        Performs an HKDF extract operation as specified in RFC 5869.
        Parameters:
        salt - the salt to use
        ikm - initial keying material
        Returns:
        a pseudorandom key suitable for use in expand operations
        Throws:
        java.security.InvalidKeyException - if the salt is not suitable for use as an HMAC key
        java.security.NoSuchAlgorithmException - if the Mac algorithm is no longer available

      • expand

        public byte[] expand​(byte[] prk,
                     byte[] info,
                     int length)
              throws java.security.InvalidKeyException,
                     java.security.NoSuchAlgorithmException
        Performs an HKDF expand operation as specified in RFC 5869.
        Parameters:
        prk - a pseudorandom key of at least HashLen octets, usually the output from the extract step. Where HashLen is the key size of the underlying Mac
        info - optional context and application specific information, can be zero length
        length - length of output keying material in bytes (<= 255*HashLen)
        Returns:
        output of keying material of length bytes
        Throws:
        java.security.InvalidKeyException - if prk is not suitable for use as an HMAC key
        java.lang.IllegalArgumentException - if length is out of the allowed range
        java.security.NoSuchAlgorithmException - if the Mac algorithm is no longer available

      • getMac

        private javax.crypto.Mac getMac​(byte[] key)
                         throws java.security.InvalidKeyException,
                                java.security.NoSuchAlgorithmException
        Throws:
        java.security.InvalidKeyException
        java.security.NoSuchAlgorithmException