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gnu.javax.crypto.key.srp6
Class SRP6KeyAgreement  view SRP6KeyAgreement download SRP6KeyAgreement.java

java.lang.Object
  extended bygnu.javax.crypto.key.BaseKeyAgreementParty
      extended bygnu.javax.crypto.key.srp6.SRP6KeyAgreement
All Implemented Interfaces:
gnu.javax.crypto.key.IKeyAgreementParty
Direct Known Subclasses:
SRP6Host, SRP6TLSClient, SRP6TLSServer, SRP6User

public abstract class SRP6KeyAgreement
extends gnu.javax.crypto.key.BaseKeyAgreementParty

The Secure Remote Password (SRP) key agreement protocol, also known as SRP-6, is designed by Thomas J. Wu (see references). The protocol, and its elements are described as follows:

 N    A large safe prime (N = 2q+1, where q is prime)
      All arithmetic is done modulo N.
 g    A generator modulo N
 s    User's salt
 I    Username
 p    Cleartext Password
 H()  One-way hash function
 ^    (Modular) Exponentiation
 u    Random scrambling parameter
 a,b  Secret ephemeral values
 A,B  Public ephemeral values
 x    Private key (derived from p and s)
 v    Password verifier

 The host stores passwords using the following formula:
 x = H(s | H(I ":" p))           (s is chosen randomly)
 v = g^x                   (computes password verifier)

 The host then keeps {I, s, v} in its password database.

 The authentication protocol itself goes as follows:
 User -> Host:  I, A = g^a         (identifies self, a = random number)
 Host -> User:  s, B = 3v + g^b    (sends salt, b = random number)

 Both:  u = H(A, B)

 User:  x = H(s, p)                (user enters password)
 User:  S = (B - 3g^x) ^ (a + ux)  (computes session key)
 User:  K = H(S)

 Host:  S = (Av^u) ^ b             (computes session key)
 Host:  K = H(S)
 

Reference:

  1. SRP Protocol Design
    Thomas J. Wu.


Field Summary
protected  java.math.BigInteger g
           
static java.lang.String GENERATOR
           
static java.lang.String HASH_FUNCTION
           
static java.lang.String HOST_PASSWORD_DB
           
protected  java.math.BigInteger K
          The shared secret key.
protected  java.math.BigInteger N
           
static java.lang.String SHARED_MODULUS
           
static java.lang.String SOURCE_OF_RANDOMNESS
           
protected  gnu.javax.crypto.sasl.srp.SRP srp
           
protected static java.math.BigInteger THREE
           
static java.lang.String USER_IDENTITY
           
static java.lang.String USER_PASSWORD
           
 
Fields inherited from class gnu.javax.crypto.key.BaseKeyAgreementParty
complete, initialised, irnd, name, rnd, step, TWO
 
Constructor Summary
protected SRP6KeyAgreement()
           
 
Method Summary
protected  void engineReset()
           
protected  byte[] engineSharedSecret()
           
protected  java.math.BigInteger uValue(java.math.BigInteger A, java.math.BigInteger B)
           
 
Methods inherited from class gnu.javax.crypto.key.BaseKeyAgreementParty
engineInit, engineProcessMessage, getSharedSecret, init, isComplete, name, nextRandomBytes, processMessage, reset
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

SOURCE_OF_RANDOMNESS

public static final java.lang.String SOURCE_OF_RANDOMNESS
See Also:
Constant Field Values

SHARED_MODULUS

public static final java.lang.String SHARED_MODULUS
See Also:
Constant Field Values

GENERATOR

public static final java.lang.String GENERATOR
See Also:
Constant Field Values

HASH_FUNCTION

public static final java.lang.String HASH_FUNCTION
See Also:
Constant Field Values

USER_IDENTITY

public static final java.lang.String USER_IDENTITY
See Also:
Constant Field Values

USER_PASSWORD

public static final java.lang.String USER_PASSWORD
See Also:
Constant Field Values

HOST_PASSWORD_DB

public static final java.lang.String HOST_PASSWORD_DB
See Also:
Constant Field Values

THREE

protected static final java.math.BigInteger THREE

srp

protected gnu.javax.crypto.sasl.srp.SRP srp

N

protected java.math.BigInteger N

g

protected java.math.BigInteger g

K

protected java.math.BigInteger K
The shared secret key.

Constructor Detail

SRP6KeyAgreement

protected SRP6KeyAgreement()
Method Detail

engineSharedSecret

protected byte[] engineSharedSecret()
                             throws gnu.javax.crypto.key.KeyAgreementException

engineReset

protected void engineReset()

uValue

protected java.math.BigInteger uValue(java.math.BigInteger A,
                                      java.math.BigInteger B)