|
|||||||||
PREV CLASS NEXT CLASS | FRAMES NO FRAMES | ||||||||
SUMMARY: INNER | FIELD | CONSTR | METHOD | DETAIL: FIELD | CONSTR | METHOD |
java.lang.Object | +--org.logi.crypto.Crypto | +--org.logi.crypto.keys.K | +--org.logi.crypto.keys.DHKey
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.
DHKeyExNoninter
Fields inherited from class org.logi.crypto.Crypto |
BIT, cdsPath, EMPTY_ARRAY, FOUR, keySource, NIBBLE, ONE, primeCertainty, random, TWO, ZERO |
Constructor Summary | |
DHKey(java.math.BigInteger x,
java.math.BigInteger g,
java.math.BigInteger m,
boolean pri)
Create a new Diffie-Hellman key object. |
|
DHKey(int n)
Create a random private DHKey with an n
bit modulus. |
|
DHKey(java.lang.String username,
java.lang.String password,
java.lang.String hashFunction,
int n)
Create a private Diffie-Hellman key from a username/password pair using an n-bit modulus. |
Method Summary | |
int |
cipherBlockSize()
Returns the size of the blocks that can be decrypted in one call to decrypt(). |
static KeyPair |
createKeys(int n)
Create a pair of public/private keys in a group with an n bit modulo. |
static KeyPair |
createKeys(java.lang.String username,
java.lang.String password,
java.lang.String hashFunction,
int n)
Create a pair of public/private keys in a group with an n bit modulo. |
void |
decrypt(byte[] source,
int i,
byte[] dest,
int j)
Decrypt one block of data. |
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". |
java.math.BigInteger |
getG()
Return the generator for this key. |
static java.math.BigInteger |
getGenerator(java.math.BigInteger m)
Return a Generator for a modulus group. |
java.math.BigInteger |
getKey()
Return the BigInteger representing this key. |
java.math.BigInteger |
getM()
Return the modulus for this key. |
static java.math.BigInteger |
getModulus(int n)
Return a Diffie-Hellman modulus. |
DHKey |
getPublic()
Return the public key from the pair. |
int |
getSize()
Return the "size" of the key. |
boolean |
isPrivate()
Returns true iff this is a private key. |
boolean |
matches(Key key)
Check if a key mathces this. |
static DHKey |
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. |
Signature |
sign(Fingerprint fp)
Create a signature for a Fingerprint fith a private key. |
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.keys.K |
getFingerprint, getFingerprint, hashCode, matchFingerprint, matchFingerprint |
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.PrettyPrintable |
prettyPrint |
Constructor Detail |
public DHKey(java.math.BigInteger x, java.math.BigInteger g, java.math.BigInteger m, boolean pri)
x
in the group modulo m
with generator
g
. It is a private key iff pri is
true
.
public DHKey(int n)
n
bit modulus.
Pre-calcualted modula exist for bit lengths 256, 512, 1024 and 2048. Using these values saves a lot of time and does not weaken the keys.
public DHKey(java.lang.String username, java.lang.String password, java.lang.String hashFunction, int n) throws InvalidCDSException
The key is created by hashing the password, appending with
0
's until it is n-1
bits long.
The hashFunction parameters directs which hash function to use. It must be the name of a supported hash function, such as MD5 or SHA1.
The username
does not need to be secret and can in
fact be a fixed string. It plays a similar role as SALT in unix
password systems in protecting against dictionary attacks.
Pre-calcualted modula exist for bit lengths 256, 512, 1024 and 2048. Using these values saves a lot of time and does not weaken the keys.
InvalidCDSException
- if the specified hash function is not available.Method Detail |
public static DHKey parseCDS(java.lang.String[] param) throws InvalidCDSException
A valid CDS can be created by calling the toString() method.
InvalidCDSException
- if the CDS is malformed.Crypto.fromString(String)
public static java.math.BigInteger getModulus(int n)
Return the largest prime p
< 2^n
such
that (p
-1)/2 is prime. This takes a long time unless
n
is one of 256, 512, 1024 or 2048.
The reason for the second constraint on p
is to make
the Discrete-Logarithm problem harder in the group Z_p. In
particular it thwarts the Pholig-Hellman algorithm.
public static java.math.BigInteger getGenerator(java.math.BigInteger m)
Returns the smallest number g
> 1 with
gcd(g
,m-1
)=1.
public static KeyPair createKeys(int n)
n
bit modulo.
Pre-calcualted modula exist for bit lengths 256, 512, 1024 and 2048. Using these values saves a lot of time and does not weaken the keys.
public static KeyPair createKeys(java.lang.String username, java.lang.String password, java.lang.String hashFunction, int n) throws InvalidCDSException
n
bit modulo.
Pre-calcualted modula exist for bit lengths 256, 512, 1024 and 2048. Using these values saves a lot of time and does not weaken the keys.
public int getSize()
getSize
in interface Key
public java.lang.String getAlgorithm()
getAlgorithm
in interface Key
public boolean isPrivate()
isPrivate
in interface Key
public DHKey getPublic()
public java.math.BigInteger getKey()
public java.math.BigInteger getM()
public java.math.BigInteger getG()
public final boolean equals(java.lang.Object o)
equals
in class java.lang.Object
public boolean matches(Key key)
matches
in interface Key
public java.lang.String toString()
toString
in class java.lang.Object
public void prettyPrint(java.io.PrintWriter out, int ind, int rec) throws java.io.IOException
prettyPrint
in interface PrettyPrintable
prettyPrint
in class Crypto
public int plainBlockSize()
plainBlockSize
in interface CipherKey
public int cipherBlockSize()
cipherBlockSize
in interface CipherKey
public void encrypt(byte[] source, int i, byte[] dest, int j)
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()
.
encrypt
in interface CipherKey
public void decrypt(byte[] source, int i, byte[] dest, int j)
source
starting at offset i
and
plaintext is written to dest
, starting at
offset j
.
The amount of data read and written will match the values returned
by cipherBlockSize()
and plainBlockSize()
.
decrypt
in interface CipherKey
public int signBlockSize()
signBlockSize
in interface SignatureKey
public int signatureSize()
signatureSize
in interface SignatureKey
public Signature sign(Fingerprint fp) throws KeyException
sign
in interface SignatureKey
KeyException
- if the key modulus is shorter than the signature.KeyException
- if this is not a private keypublic boolean verify(Signature s, Fingerprint fp) throws KeyException
The method returns true iff s
is a signature for
fp
created with the mathcin private key.
verify
in interface SignatureKey
KeyException
- if this is not a public key
|
|||||||||
PREV CLASS NEXT CLASS | FRAMES NO FRAMES | ||||||||
SUMMARY: INNER | FIELD | CONSTR | METHOD | DETAIL: FIELD | CONSTR | METHOD |