org.logi.crypto.keys
Class DHPublicKey

java.lang.Object
  |
  +--org.logi.crypto.Crypto
        |
        +--org.logi.crypto.keys.K
              |
              +--org.logi.crypto.keys.DHPublicKey

All Implemented Interfaces:

EncryptionKey, Key, java.security.Key, PrettyPrintable, java.io.Serializable, VerificationKey

public class DHPublicKey

extends org.logi.crypto.keys.K

implements EncryptionKey, VerificationKey

This object holds one Diffie-Hellman key. They can be used for Diffie-Hellman key-exchange with the DHKeyExNoninter and related classes or directly for encryption and signatures, in which case it uses the ElGamal algorithm.

The modulus and generator for the group from which the key is chosen are fixed for a given key-size. They are pre-calculated for a few bit-sizes, but take long to claculate for others.

The CDS for a Diffie-Hellman key is DHKey(x,g,m,pub) for a public key or DHKey(x,g,m,pri) for a private key. In both cases x,g and m are hexadecimal numbers.

Author:

Logi Ragnarsson (logir@logi.org)

See Also:

DHKeyExNoninter, Serialized Form

Fields inherited from class org.logi.crypto.Crypto

BIT, cdsPath, EMPTY_ARRAY, FOUR, keySource, NIBBLE, ONE, primeCertainty, random, TWO, ZERO

Fields inherited from interface java.security.Key

serialVersionUID

Constructor Summary

DHPublicKey(java.math.BigInteger y, java.math.BigInteger g, java.math.BigInteger m)
Create a new Diffie-Hellman key object.

Method Summary

int	cipherBlockSize() Returns the size of the blocks that can be decrypted in one call to decrypt().
void	encrypt(byte[] source, int i, byte[] dest, int j) Encrypt one block of data.
boolean	equals(java.lang.Object o) Return true iff the two keys are equivalent.
java.lang.String	getAlgorithm() The name of the algorithm is "Diffie-Hellman".
byte[]	getEncoded() Return encoded version.
Fingerprint	getFingerprint() Return the key's fingerprint using the default hash function.
Fingerprint	getFingerprint(java.lang.String algorithm) Return the key's fingerprint using the specified hash function.
java.lang.String	getFormat() Returns the name of the key-encoding format.
java.math.BigInteger	getG() Return the generator for this key.
java.math.BigInteger	getM() Return the modulus for this key.
int	getSize() Return the "size" of the key.
java.math.BigInteger	getY() Return y.
int	hashCode() Return a hash-code based on the keys SHA1 fingerprint.
boolean	matches(Key key) Check if a key mathces this.
Fingerprint	matchFingerprint() Returns the default fingerprint of the matching key in the key-pair.
Fingerprint	matchFingerprint(java.lang.String algorithm) Returns the default fingerprint of the matching key in the key-pair.
static DHPublicKey	parseCDS(java.lang.String[] param) Used by Crypto.fromString when parsing a CDS.
int	plainBlockSize() Returns the size of the blocks that can be encrypted in one call to encrypt().
void	prettyPrint(java.io.PrintWriter out, int ind, int rec) Print this object to out, indented with ind tabs, going down at most rec levels of recursion.
int	signatureSize() Returns the length of a signature in bytes.
int	signBlockSize() Returns the maximum size in bytes of the fingerprints that can be signed.
java.lang.String	toString() Return a CDS for this key.
boolean	verify(Signature s, Fingerprint fp) Verify a Signature on a Fingerprint with a public key.

Methods inherited from class org.logi.crypto.Crypto

binString, binString, ensureArrayLength, ensureArrayLength, equal, equalRelaxed, equalSub, fromHexNibble, fromHexString, fromString, fromString, hexString, hexString, hexString, hexString, hexString, initRandom, initRandom, makeClass, makeInt, makeLong, makeSessionKey, pastSpace, pickBits, pickBits, prettyPrint, readBlock, readInt, trimArrayLength, trimArrayLength, trimLeadingZeroes, writeBytes, writeBytes, writeInt

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface org.logi.crypto.keys.Key

getFingerprint, getFingerprint, hashCode, matchFingerprint, matchFingerprint

Methods inherited from interface org.logi.crypto.io.PrettyPrintable

prettyPrint

Methods inherited from interface java.security.Key

getEncoded, getFormat

Constructor Detail

DHPublicKey

public DHPublicKey(java.math.BigInteger y,
                   java.math.BigInteger g,
                   java.math.BigInteger m)

Create a new Diffie-Hellman key object. An object is created for x in the group modulo m with generator g. It is a private key iff pri is true.

Method Detail

parseCDS

public static DHPublicKey parseCDS(java.lang.String[] param)
                            throws InvalidCDSException

Used by Crypto.fromString when parsing a CDS.

A valid CDS can be created by calling the toString() method.

Throws:

InvalidCDSException - if the CDS is malformed.

See Also:

Crypto.fromString(String)

getSize

public int getSize()

Return the "size" of the key. This is a (fairly inaccurate) measure of how difficult it is to break and is heavily dependant on the algorithm used.

Specified by:

getSize in interface Key

getAlgorithm

public java.lang.String getAlgorithm()

The name of the algorithm is "Diffie-Hellman".

Specified by:

getAlgorithm in interface Key

getY

public java.math.BigInteger getY()

Return y.

getM

public java.math.BigInteger getM()

Return the modulus for this key.

getG

public java.math.BigInteger getG()

Return the generator for this key.

equals

public final boolean equals(java.lang.Object o)

Return true iff the two keys are equivalent.

Overrides:

equals in class java.lang.Object

matches

public boolean matches(Key key)

Check if a key mathces this. This is true if this and key are a matched pair of public/private.

Specified by:

matches in interface Key

toString

public java.lang.String toString()

Return a CDS for this key.

Overrides:

toString in class java.lang.Object

prettyPrint

public void prettyPrint(java.io.PrintWriter out,
                        int ind,
                        int rec)
                 throws java.io.IOException

Print this object to out, indented with ind tabs, going down at most rec levels of recursion.

Specified by:

prettyPrint in interface PrettyPrintable

Overrides:

prettyPrint in class Crypto

plainBlockSize

public int plainBlockSize()

Returns the size of the blocks that can be encrypted in one call to encrypt(). For ElGamal keys this depends on the size of the key.

Specified by:

plainBlockSize in interface EncryptionKey

cipherBlockSize

public int cipherBlockSize()

Returns the size of the blocks that can be decrypted in one call to decrypt(). For ElGamal keys this depends on the size of the key.

Specified by:

cipherBlockSize in interface EncryptionKey

encrypt

public void encrypt(byte[] source,
                    int i,
                    byte[] dest,
                    int j)

Encrypt one block of data. The plaintext is taken from source starting at offset i and ciphertext is written to dest, starting at offset j.

The amount of data read and written will match the values returned by plainBlockSize() and cipherBlockSize().

Specified by:

encrypt in interface EncryptionKey

signBlockSize

public int signBlockSize()

Returns the maximum size in bytes of the fingerprints that can be signed.

Specified by:

signBlockSize in interface VerificationKey

signatureSize

public int signatureSize()

Returns the length of a signature in bytes.

Specified by:

signatureSize in interface VerificationKey

verify

public boolean verify(Signature s,
                      Fingerprint fp)
               throws KeyException

Verify a Signature on a Fingerprint with a public key.

The method returns true iff s is a signature for fp created with the mathcin private key.

Specified by:

verify in interface VerificationKey

Throws:

KeyException - if this is not a public key

getFingerprint

public final Fingerprint getFingerprint()

Return the key's fingerprint using the default hash function.

Specified by:

getFingerprint in interface Key

getFingerprint

public final Fingerprint getFingerprint(java.lang.String algorithm)
                                 throws InvalidCDSException

Return the key's fingerprint using the specified hash function.

Specified by:

getFingerprint in interface Key

Throws:

InvalidCDSException - if the specified hash function is not available.

matchFingerprint

public Fingerprint matchFingerprint()

Returns the default fingerprint of the matching key in the key-pair.

Specified by:

matchFingerprint in interface Key

matchFingerprint

public Fingerprint matchFingerprint(java.lang.String algorithm)
                             throws InvalidCDSException

Returns the default fingerprint of the matching key in the key-pair.

Specified by:

matchFingerprint in interface Key

Throws:

InvalidCDSException - if the specified hash function is not available.

hashCode

public final int hashCode()

Return a hash-code based on the keys SHA1 fingerprint.

Specified by:

hashCode in interface Key

Overrides:

hashCode in class java.lang.Object

getEncoded

public byte[] getEncoded()

Return encoded version.

Specified by:

getEncoded in interface java.security.Key

getFormat

public java.lang.String getFormat()

Returns the name of the key-encoding format.

Specified by:

getFormat in interface java.security.Key