org.logi.crypto.keys
Class CaesarKey

java.lang.Object
  |
  +--org.logi.crypto.Crypto
        |
        +--org.logi.crypto.keys.K
              |
              +--org.logi.crypto.keys.SymmetricKey
                    |
                    +--org.logi.crypto.keys.CaesarKey
All Implemented Interfaces:
CipherKey, DecryptionKey, EncryptionKey, Key, java.security.Key, PrettyPrintable, java.io.Serializable

public final class CaesarKey
extends org.logi.crypto.keys.SymmetricKey
implements CipherKey

The Caesar algorithm is supposedly the one Julius Caesar used by hand many centuries ago. As you can imagine, this is NOT A STRONG CIPHER, but included only to show how to write a very simple Key class for the logi.crypto package. Often, the first assignment given to cryptography students is to break this cipher given no known plaintext.

Data is encrypted byte-by-byte by adding a constant value to it and taking the 8 lowest order bits.

The CDS for a CaesarKey object is CaesarKey(n) where n is a value in the range 0..255.

Author:
Logi Ragnarsson (logir@logi.org)
See Also:
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
CaesarKey()
          Create a new random Caesar key.
CaesarKey(byte shift)
          Create a new Caesar key with the specified shift.
 
Method Summary
 int cipherBlockSize()
          The block-size for the Caesar cipher is one byte.
 void decrypt(byte[] source, int i, byte[] dest, int j)
          Decrypt one byte.
 void encrypt(byte[] source, int i, byte[] dest, int j)
          Encrypt one byte.
 boolean equals(java.lang.Object o)
          Return true iff the two keys are equivalent.
 java.lang.String getAlgorithm()
          The name of the algorithm is "Caesar".
 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.
 int getSize()
          The key-size for the Caesar cipher is 1 byte.
 int hashCode()
          Return a hash-code based on the keys SHA1 fingerprint.
 boolean matches(Key key)
          Returns true if this and key are the same symmetric key.
 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 CaesarKey parseCDS(java.lang.String[] param)
          Used by Crypto.fromString when parsing a CDS.
 int plainBlockSize()
          The block-size for the Caesar cipher is one byte.
 java.lang.String toString()
          Return a CDS for this 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, 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, matches, matchFingerprint, matchFingerprint
 
Methods inherited from interface org.logi.crypto.io.PrettyPrintable
prettyPrint, prettyPrint
 
Methods inherited from interface java.security.Key
getEncoded, getFormat
 

Constructor Detail

CaesarKey

public CaesarKey(byte shift)
Create a new Caesar key with the specified shift.

CaesarKey

public CaesarKey()
Create a new random Caesar key.
Method Detail

parseCDS

public static CaesarKey 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()
The key-size for the Caesar cipher is 1 byte.
Specified by:
getSize in interface Key

plainBlockSize

public final int plainBlockSize()
The block-size for the Caesar cipher is one byte.
Specified by:
plainBlockSize in interface EncryptionKey

cipherBlockSize

public final int cipherBlockSize()
The block-size for the Caesar cipher is one byte.
Specified by:
cipherBlockSize in interface EncryptionKey

getAlgorithm

public java.lang.String getAlgorithm()
The name of the algorithm is "Caesar".
Specified by:
getAlgorithm in interface 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

toString

public java.lang.String toString()
Return a CDS for this key.
Overrides:
toString in class java.lang.Object
See Also:
Crypto.fromString(java.io.Reader)

encrypt

public final void encrypt(byte[] source,
                          int i,
                          byte[] dest,
                          int j)
Encrypt one byte. source[i] is encrypted and put in dest[j].
Specified by:
encrypt in interface EncryptionKey

decrypt

public final void decrypt(byte[] source,
                          int i,
                          byte[] dest,
                          int j)
Decrypt one byte. source[i] is decrypted and put in dest[j].
Specified by:
decrypt in interface DecryptionKey

matches

public boolean matches(Key key)
Returns true if this and key are the same symmetric key.

Symmetric keys simply call equals(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


Copyright (c) 1997-2001 Logi Ragnarsson - Distributed under the GPL