Package org.bouncycastle.crypto.agreement.jpake

Class JPAKEUtil

  • public class JPAKEUtil
extends java.lang.Object
    Primitives needed for a J-PAKE exchange.

    The recommended way to perform a J-PAKE exchange is by using two JPAKEParticipants. Internally, those participants call these primitive operations in JPAKEUtil.

    The primitives, however, can be used without a JPAKEParticipant if needed.

    • Constructor Summary

      Constructors 
      Constructor Description
      JPAKEUtil()  

    • Method Summary

      All Methods Static Methods Concrete Methods 
      Modifier and Type Method Description
      static java.math.BigInteger calculateA​(java.math.BigInteger p, java.math.BigInteger q, java.math.BigInteger gA, java.math.BigInteger x2s)
      Calculate A as done in round 2.
      static java.math.BigInteger calculateGA​(java.math.BigInteger p, java.math.BigInteger gx1, java.math.BigInteger gx3, java.math.BigInteger gx4)
      Calculate ga as done in round 2.
      static java.math.BigInteger calculateGx​(java.math.BigInteger p, java.math.BigInteger g, java.math.BigInteger x)
      Calculate g^x mod p as done in round 1.
      static java.math.BigInteger calculateKeyingMaterial​(java.math.BigInteger p, java.math.BigInteger q, java.math.BigInteger gx4, java.math.BigInteger x2, java.math.BigInteger s, java.math.BigInteger B)
      Calculates the keying material, which can be done after round 2 has completed.
      static java.math.BigInteger calculateMacTag​(java.lang.String participantId, java.lang.String partnerParticipantId, java.math.BigInteger gx1, java.math.BigInteger gx2, java.math.BigInteger gx3, java.math.BigInteger gx4, java.math.BigInteger keyingMaterial, Digest digest)
      Calculates the MacTag (to be used for key confirmation), as defined by NIST SP 800-56A Revision 1, Section 8.2 Unilateral Key Confirmation for Key Agreement Schemes.
      static java.math.BigInteger calculateS​(char[] password)
      Converts the given password to a BigInteger for use in arithmetic calculations.
      static java.math.BigInteger calculateX2s​(java.math.BigInteger q, java.math.BigInteger x2, java.math.BigInteger s)
      Calculate x2 * s as done in round 2.
      static java.math.BigInteger[] calculateZeroKnowledgeProof​(java.math.BigInteger p, java.math.BigInteger q, java.math.BigInteger g, java.math.BigInteger gx, java.math.BigInteger x, java.lang.String participantId, Digest digest, java.security.SecureRandom random)
      Calculate a zero knowledge proof of x using Schnorr's signature.
      static java.math.BigInteger generateX1​(java.math.BigInteger q, java.security.SecureRandom random)
      Return a value that can be used as x1 or x3 during round 1.
      static java.math.BigInteger generateX2​(java.math.BigInteger q, java.security.SecureRandom random)
      Return a value that can be used as x2 or x4 during round 1.
      static void validateGa​(java.math.BigInteger ga)
      Validates that ga is not 1.
      static void validateGx4​(java.math.BigInteger gx4)
      Validates that g^x4 is not 1.
      static void validateMacTag​(java.lang.String participantId, java.lang.String partnerParticipantId, java.math.BigInteger gx1, java.math.BigInteger gx2, java.math.BigInteger gx3, java.math.BigInteger gx4, java.math.BigInteger keyingMaterial, Digest digest, java.math.BigInteger partnerMacTag)
      Validates the MacTag received from the partner participant.
      static void validateNotNull​(java.lang.Object object, java.lang.String description)
      Validates that the given object is not null.
      static void validateParticipantIdsDiffer​(java.lang.String participantId1, java.lang.String participantId2)
      Validates that the given participant ids are not equal.
      static void validateParticipantIdsEqual​(java.lang.String expectedParticipantId, java.lang.String actualParticipantId)
      Validates that the given participant ids are equal.
      static void validateZeroKnowledgeProof​(java.math.BigInteger p, java.math.BigInteger q, java.math.BigInteger g, java.math.BigInteger gx, java.math.BigInteger[] zeroKnowledgeProof, java.lang.String participantId, Digest digest)
      Validates the zero knowledge proof (generated by calculateZeroKnowledgeProof(BigInteger, BigInteger, BigInteger, BigInteger, BigInteger, String, Digest, SecureRandom)) is correct.

      • Methods inherited from class java.lang.Object

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

    • Constructor Detail

      • JPAKEUtil

        public JPAKEUtil()

    • Method Detail

      • generateX1

        public static java.math.BigInteger generateX1​(java.math.BigInteger q,
                                              java.security.SecureRandom random)
        Return a value that can be used as x1 or x3 during round 1.

        The returned value is a random value in the range [0, q-1].

      • generateX2

        public static java.math.BigInteger generateX2​(java.math.BigInteger q,
                                              java.security.SecureRandom random)
        Return a value that can be used as x2 or x4 during round 1.

        The returned value is a random value in the range [1, q-1].

      • calculateS

        public static java.math.BigInteger calculateS​(char[] password)
        Converts the given password to a BigInteger for use in arithmetic calculations.

      • calculateGx

        public static java.math.BigInteger calculateGx​(java.math.BigInteger p,
                                               java.math.BigInteger g,
                                               java.math.BigInteger x)
        Calculate g^x mod p as done in round 1.

      • calculateGA

        public static java.math.BigInteger calculateGA​(java.math.BigInteger p,
                                               java.math.BigInteger gx1,
                                               java.math.BigInteger gx3,
                                               java.math.BigInteger gx4)
        Calculate ga as done in round 2.

      • calculateX2s

        public static java.math.BigInteger calculateX2s​(java.math.BigInteger q,
                                                java.math.BigInteger x2,
                                                java.math.BigInteger s)
        Calculate x2 * s as done in round 2.

      • calculateA

        public static java.math.BigInteger calculateA​(java.math.BigInteger p,
                                              java.math.BigInteger q,
                                              java.math.BigInteger gA,
                                              java.math.BigInteger x2s)
        Calculate A as done in round 2.

      • calculateZeroKnowledgeProof

        public static java.math.BigInteger[] calculateZeroKnowledgeProof​(java.math.BigInteger p,
                                                                 java.math.BigInteger q,
                                                                 java.math.BigInteger g,
                                                                 java.math.BigInteger gx,
                                                                 java.math.BigInteger x,
                                                                 java.lang.String participantId,
                                                                 Digest digest,
                                                                 java.security.SecureRandom random)
        Calculate a zero knowledge proof of x using Schnorr's signature. The returned array has two elements {g^v, r = v-x*h} for x.

      • validateGx4

        public static void validateGx4​(java.math.BigInteger gx4)
                        throws CryptoException
        Validates that g^x4 is not 1.
        Throws:
        CryptoException - if g^x4 is 1

      • validateGa

        public static void validateGa​(java.math.BigInteger ga)
                       throws CryptoException
        Validates that ga is not 1.

        As described by Feng Hao...

        Alice could simply check ga != 1 to ensure it is a generator. In fact, as we will explain in Section 3, (x1 + x3 + x4 ) is random over Zq even in the face of active attacks. Hence, the probability for ga = 1 is extremely small - on the order of 2^160 for 160-bit q.
        Throws:
        CryptoException - if ga is 1

      • calculateKeyingMaterial

        public static java.math.BigInteger calculateKeyingMaterial​(java.math.BigInteger p,
                                                           java.math.BigInteger q,
                                                           java.math.BigInteger gx4,
                                                           java.math.BigInteger x2,
                                                           java.math.BigInteger s,
                                                           java.math.BigInteger B)
        Calculates the keying material, which can be done after round 2 has completed. A session key must be derived from this key material using a secure key derivation function (KDF). The KDF used to derive the key is handled externally (i.e. not by JPAKEParticipant). 
         KeyingMaterial = (B/g^{x2*x4*s})^x2

      • validateParticipantIdsDiffer

        public static void validateParticipantIdsDiffer​(java.lang.String participantId1,
                                                java.lang.String participantId2)
                                         throws CryptoException
        Validates that the given participant ids are not equal. (For the J-PAKE exchange, each participant must use a unique id.)
        Throws:
        CryptoException - if the participantId strings are equal.

      • validateParticipantIdsEqual

        public static void validateParticipantIdsEqual​(java.lang.String expectedParticipantId,
                                               java.lang.String actualParticipantId)
                                        throws CryptoException
        Validates that the given participant ids are equal. This is used to ensure that the payloads received from each round all come from the same participant.
        Throws:
        CryptoException - if the participantId strings are equal.

      • validateNotNull

        public static void validateNotNull​(java.lang.Object object,
                                   java.lang.String description)
        Validates that the given object is not null.
        Parameters:
        object - object in question
        description - name of the object (to be used in exception message)
        Throws:
        java.lang.NullPointerException - if the object is null.

      • calculateMacTag

        public static java.math.BigInteger calculateMacTag​(java.lang.String participantId,
                                                   java.lang.String partnerParticipantId,
                                                   java.math.BigInteger gx1,
                                                   java.math.BigInteger gx2,
                                                   java.math.BigInteger gx3,
                                                   java.math.BigInteger gx4,
                                                   java.math.BigInteger keyingMaterial,
                                                   Digest digest)
        Calculates the MacTag (to be used for key confirmation), as defined by NIST SP 800-56A Revision 1, Section 8.2 Unilateral Key Confirmation for Key Agreement Schemes. 
         MacTag = HMAC(MacKey, MacLen, MacData)

 MacKey = H(K || "JPAKE_KC")

 MacData = "KC_1_U" || participantId || partnerParticipantId || gx1 || gx2 || gx3 || gx4

 Note that both participants use "KC_1_U" because the sender of the round 3 message
 is always the initiator for key confirmation.

 HMAC = HMac used with the given Digest
 H = The given Digest
 MacLen = length of MacTag

      • validateMacTag

        public static void validateMacTag​(java.lang.String participantId,
                                  java.lang.String partnerParticipantId,
                                  java.math.BigInteger gx1,
                                  java.math.BigInteger gx2,
                                  java.math.BigInteger gx3,
                                  java.math.BigInteger gx4,
                                  java.math.BigInteger keyingMaterial,
                                  Digest digest,
                                  java.math.BigInteger partnerMacTag)
                           throws CryptoException
        Validates the MacTag received from the partner participant.
        Parameters:
        partnerMacTag - the MacTag received from the partner.
        Throws:
        CryptoException - if the participantId strings are equal.