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The Bouncy Castle Crypto package is a Java implementation of cryptographic algorithms. This jar contains JCE provider and lightweight API for the Bouncy Castle Cryptography APIs for JDK 1.5 and up.

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package org.bouncycastle.crypto.agreement.jpake;

import java.math.BigInteger;

/**
 * A pre-computed prime order group for use during a J-PAKE exchange.
 * 

* Typically a Schnorr group is used. In general, J-PAKE can use any prime order group * that is suitable for public key cryptography, including elliptic curve cryptography. *

* See {@link JPAKEPrimeOrderGroups} for convenient standard groups. *

* NIST publishes * many groups that can be used for the desired level of security. */ public class JPAKEPrimeOrderGroup { private final BigInteger p; private final BigInteger q; private final BigInteger g; /** * Constructs a new {@link JPAKEPrimeOrderGroup}. *

* In general, you should use one of the pre-approved groups from * {@link JPAKEPrimeOrderGroups}, rather than manually constructing one. *

* The following basic checks are performed: *

    *
  • p-1 must be evenly divisible by q
  • *
  • g must be in [2, p-1]
  • *
  • g^q mod p must equal 1
  • *
  • p must be prime (within reasonably certainty)
  • *
  • q must be prime (within reasonably certainty)
  • *
*

* The prime checks are performed using {@link BigInteger#isProbablePrime(int)}, * and are therefore subject to the same probability guarantees. *

* These checks prevent trivial mistakes. * However, due to the small uncertainties if p and q are not prime, * advanced attacks are not prevented. * Use it at your own risk. * * @throws NullPointerException if any argument is null * @throws IllegalArgumentException if any of the above validations fail */ public JPAKEPrimeOrderGroup(BigInteger p, BigInteger q, BigInteger g) { /* * Don't skip the checks on user-specified groups. */ this(p, q, g, false); } /** * Internal package-private constructor used by the pre-approved * groups in {@link JPAKEPrimeOrderGroups}. * These pre-approved groups can avoid the expensive checks. */ JPAKEPrimeOrderGroup(BigInteger p, BigInteger q, BigInteger g, boolean skipChecks) { JPAKEUtil.validateNotNull(p, "p"); JPAKEUtil.validateNotNull(q, "q"); JPAKEUtil.validateNotNull(g, "g"); if (!skipChecks) { if (!p.subtract(JPAKEUtil.ONE).mod(q).equals(JPAKEUtil.ZERO)) { throw new IllegalArgumentException("p-1 must be evenly divisible by q"); } if (g.compareTo(BigInteger.valueOf(2)) == -1 || g.compareTo(p.subtract(JPAKEUtil.ONE)) == 1) { throw new IllegalArgumentException("g must be in [2, p-1]"); } if (!g.modPow(q, p).equals(JPAKEUtil.ONE)) { throw new IllegalArgumentException("g^q mod p must equal 1"); } /* * Note that these checks do not guarantee that p and q are prime. * We just have reasonable certainty that they are prime. */ if (!p.isProbablePrime(20)) { throw new IllegalArgumentException("p must be prime"); } if (!q.isProbablePrime(20)) { throw new IllegalArgumentException("q must be prime"); } } this.p = p; this.q = q; this.g = g; } public BigInteger getP() { return p; } public BigInteger getQ() { return q; } public BigInteger getG() { return g; } }





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