iaik.security.rsa
Class RSAPrivateKey

java.lang.Object
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  +--iaik.pkcs.pkcs8.PrivateKeyInfo
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        +--iaik.security.rsa.RSAPrivateKey

public class RSAPrivateKey

extends PrivateKeyInfo

implements RSAPrivateCrtKey, java.io.Serializable, java.lang.Cloneable

This class implements an RSA private key and supports ASN.1 encoding.

This class extends iaik.pkcs.pkcs8.PrivateKeyInfo for supporting the PKCS#8 Private Key Information Standard for RSA private keys. This class implements the java.security.interfaces.RSAPrivateKeyCrt interface for providing the functionality of a private key, as used for data decrypting or digital signing based on the RSA algorithm. This class implements the RSAPrivateKeyCrt interface for using the Chinese Remainder Theorem to speed up private key operations by extending the standard RSA private key components modulus n and private exponent d according to PKCS#1:

 RSAPrivateKey ::= SEQUENCE {
   version Version, -- a INTEGER version number; 0 for this standard
   modulus INTEGER, -- n
   publicExponent INTEGER, -- e 
   privateExponent INTEGER, -- d
   prime1 INTEGER, -- primeP (p) (first prime factor of n)
   prime2 INTEGER, -- primeQ (q) (second prime factor of n)
   exponent1 INTEGER, -- primeExponentP: d mod (p - 1)
   exponent2 INTEGER, -- primeExponentQ: d mod (q - 1)
   crtCoefficient INTEGER -- Chinese Remainder Theorem ((inverse of q) mod p) }
 

An application wishing to create a RSAPrivateKey to be used for, e.g. data decryption or digital signing with the RSA algorithm, uses a proper getInstance method of the java.security.KeyPairGenerator class, which subsequently maybe casted to RSAKeyPairGenerator for performing an algorithm-specific initialization with proper RSA parameters. If an algorithm-specific initialization is not required, the cast to RSAKeyPairGenerator can be omitted.

Generally four steps have to be performed for creating a RSAPrivateKey by using a proper KeyPairGenerator:

• First the KeyPairGenerator has to be instantiated thereby specifying the applicationīs intention to create keys for use within the RSA algorithm:

   KeyPairGenerator key_gen = KeyPairGenerator.getInstance("RSA");
   

• Second, the KeyPairGenerator just created may be initialized using a proper initialize method. For initializing the generator to create keys with a modulus length of, e.g., 512 bits, this can be explicitly specified (when not initializing the generator explicitly, per default the modulus length is set to 1024 bits):

   key_gen.initialize(512);
   

• Third the key pair is created by calling generateKeyPair():

   KeyPair key_pair = key_gen.generateKeyPair();
   

• And finally, if there is need for the RSA private key, it has to be obtained from the key pair just created:

   RSAPrivateKey rsa_priv_key = (RSAPrivateKey)key_pair.getPrivate();
   

For performing an algorithm-specific initialization with particular RSA parameters (e.g. using a particular public exponent e), an explicit cast of the KeyPairGenerator will be necessary for obtaining a specific RSAKeyPairGenerator to be initialized with the desired RSA parameters:

 RSAKeyPairGenerator rsa_key_gen = (RSAKeyPairGenerator)key_gen;
 rsa_key_gen.initialize(512, pub_exponent, sec_random);
 

(where sec_random denotes some random seed)

Guidelines on how to create some key using a KeyPairGenerator can be found in http://java.sun.com/products/JDK/1.2/docs/guide/security/CryptoSpec.html.

See Also:

PrivateKeyInfo, RSAPrivateCrtKey, KeyPairGenerator, KeyPair, iaik.pkcs.pkcs1.RSACipher, RSAKey, RSAPublicKey, RSAKeyPairGenerator, RSAKeyFactory, Serialized Form

Fields inherited from class iaik.pkcs.pkcs8.PrivateKeyInfo

private_key_algorithm, private_key_info

Fields inherited from interface java.security.PrivateKey

serialVersionUID

Fields inherited from interface java.security.Key

serialVersionUID

Constructor Summary

protected	RSAPrivateKey() Default constructor.
	RSAPrivateKey(ASN1Object obj) Creates a new private key from an ASN1Object.
	RSAPrivateKey(java.math.BigInteger modulus, java.math.BigInteger privateExponent) Creates a new RSAPrivate key from given modulus and private exponent.
	RSAPrivateKey(java.math.BigInteger modulus, java.math.BigInteger publicExponent, java.math.BigInteger privateExponent, java.math.BigInteger primeP, java.math.BigInteger primeQ, java.math.BigInteger primeExponentP, java.math.BigInteger primeExponentQ, java.math.BigInteger crtCoefficient) Creates a RSAPrivateKey from the given values.
	RSAPrivateKey(byte[] pk) Creates a new RSAPrivateKey from a DER encoded ASN.1 data structure.
	RSAPrivateKey(java.io.InputStream is) Creates a new RSAPrivateKey from an InputStream.
	RSAPrivateKey(RSAPrivateKey key) Creates a new RSAPrivateKey from a RSAPrivateKey or RSAPrivateKeyCrt.
	RSAPrivateKey(RSAPrivateKeySpec keySpec) Creates a new RSAPrivateKey from a RSAPrivateKeySpec or RSAPrivateKeyCrtSpec.

Method Summary

java.lang.Object	clone()
java.math.BigInteger	crypt(java.math.BigInteger message) Encrypts or decrypts a BigInteger using the private key.
protected void	decode(byte[] privateKey) Decodes a DER encoded RSAPrivateKey (PKCS#1).
protected byte[]	encode() Returns this RSA private key as DER encoded byte array (PKCS#1).
java.lang.String	getAlgorithm() Returns the name of the appertaining algorithm.
java.math.BigInteger	getCrtCoefficient() Returns the Chinese Remainder Theorem coefficient of this private key.
java.math.BigInteger	getModulus() Returns the modulus of this private key.
java.math.BigInteger	getPrimeExponentP() Returns the first exponent of this private key.
java.math.BigInteger	getPrimeExponentQ() Returns the second exponent of this private key.
java.math.BigInteger	getPrimeP() Returns the first prime of this private key.
java.math.BigInteger	getPrimeQ() Returns the second prime of this private key.
java.math.BigInteger	getPrivateExponent() Returns the private exponent of this private key.
java.math.BigInteger	getPublicExponent() Returns the public exponent of this private key.
PublicKey	getPublicKey() Returns the public parts (modulus n and public exponent e of this private key.
int	hashCode() Returns a hash code for this object.
static RSAPrivateKey	parse(byte[] privateKey) This method parses a RSA private key.
java.lang.String	toString() Returns a string that represents the contents of this private key.

Methods inherited from class iaik.pkcs.pkcs8.PrivateKeyInfo

createPrivateKeyInfo, decode, equals, getEncoded, getFormat, getPrivateKey, getPrivateKey, toASN1Object, writeTo

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

RSAPrivateKey

protected RSAPrivateKey()

Default constructor.

RSAPrivateKey

public RSAPrivateKey(java.math.BigInteger modulus,
                     java.math.BigInteger privateExponent)

Creates a new RSAPrivate key from given modulus and private exponent. Public exponent, prime factors p and q, primeExponentP and primeExponentQ, and Chinese Remainder Theorem Coefficient are set to ZERO (0).

Parameters:

privateExponent - the private exponent e

modulus - the modulus n

RSAPrivateKey

public RSAPrivateKey(java.math.BigInteger modulus,
                     java.math.BigInteger publicExponent,
                     java.math.BigInteger privateExponent,
                     java.math.BigInteger primeP,
                     java.math.BigInteger primeQ,
                     java.math.BigInteger primeExponentP,
                     java.math.BigInteger primeExponentQ,
                     java.math.BigInteger crtCoefficient)

Creates a RSAPrivateKey from the given values.

Parameters:

modulus - the modulus n

publicExponent - the public exponent e

privateExponent - the private exponent d

primeP - first prime factor of the modulus

primeQ - second prime factor of the modulus

primeExponentP - privateExponent mod (primeP-1)

primeExponentQ - privateExponent mod (primeQ-1)

crtCoefficient - the Chinese Remainder Theorem coefficient (multiplic inverse of primeP mod primeQ)

RSAPrivateKey

public RSAPrivateKey(RSAPrivateKeySpec keySpec)

Creates a new RSAPrivateKey from a RSAPrivateKeySpec or RSAPrivateKeyCrtSpec. If the given key specification is an instance of RSAPrivateKeySpec the Chinese Remainder Theorem would not be considered by only parsing modulus and private exponent from the given specification and setting the other parameters to ZERO (0).
If the given key specification is an instance of RSAPrivateKeyCrtSpec, all parameters (modulus, public and private exponent, prime factors p and q, primeExponentP and primeExponentQ, and Chinese Remainder Theorem coefficient) are parsed from the given specification.

Parameters:

keySpec - the key spec

RSAPrivateKey

public RSAPrivateKey(RSAPrivateKey key)

Creates a new RSAPrivateKey from a RSAPrivateKey or RSAPrivateKeyCrt. If the given key specification is an instance of RSAPrivateKey the Chinese Remainder Theorem would not be considered by only parsing modulus and private exponent from the given specification and setting the other parameters to ZERO (0).
If the given key specification is an instance of RSAPrivateKeyCrt, all parameters (modulus, public and private exponent, prime factors p and q, primeExponentP and primeExponentQ, and Chinese Remainder Theorem coefficient) are parsed from the given specification.

Parameters:

key - the key

RSAPrivateKey

public RSAPrivateKey(byte[] pk)
              throws InvalidKeyException

Creates a new RSAPrivateKey from a DER encoded ASN.1 data structure. The following ASN.1 types are suported for the private key:

• RSAPrivateKey
• PrivateKeyInfo
• EncryptedPrivateKeyInfo

Parameters:

pk - the byte array holding the DER encoded private key ASN.1 data structure

Throws:

InvalidKeyException - if something is wrong with the key encoding

RSAPrivateKey

public RSAPrivateKey(ASN1Object obj)
              throws InvalidKeyException

Creates a new private key from an ASN1Object. The ASN1Object can be of the following type:

• RSAPrivateKey
• PrivateKeyInfo
• EncryptedPrivateKeyInfo

Parameters:

obj - the private key as ASN1Object

Throws:

InvalidKeyException - if something is wrong with the key encoding

RSAPrivateKey

public RSAPrivateKey(java.io.InputStream is)
              throws java.io.IOException,
                     InvalidKeyException

Creates a new RSAPrivateKey from an InputStream.

Parameters:

is - the input stream with the data to be read to initialize the private key

Throws:

java.io.IOException - if an I/O error occurs

InvalidKeyException - if something is wrong with the key encoding

Method Detail

decode

protected void decode(byte[] privateKey)
               throws InvalidKeyException

Decodes a DER encoded RSAPrivateKey (PKCS#1).

From the given DER encoded byte array an ASN.1 object is created and parsed for the RSAPrivateKey parameters according to PKCS#1: version, modulus n, public and private exponent (e and d), prime factor primeP of n, prime factor primeQ of n, primeExponentP (d mod(p-1)), primeExponentQ (d mod(q-1)), and crtCoefficient, the Chinese Remainder Thereom coefficient q^-1 mod p.

Overrides:

decode in class PrivateKeyInfo

Parameters:

privateKey - the RSA private key as DER encoded byte array

Throws:

InvalidKeyException - if the given key is not a RSA private key

parse

public static RSAPrivateKey parse(byte[] privateKey)
                           throws InvalidKeyException

This method parses a RSA private key. The format must be RSAPrivateKey as defined in PKCS#1.

Parameters:

privateKey - a "RAW" RSA private key

Throws:

InvalidKeyException - if the given key is not a RSA private key

crypt

public java.math.BigInteger crypt(java.math.BigInteger message)

Encrypts or decrypts a BigInteger using the private key. This method uses a fast algorithm based on the chinese remainder theorem.

Parameters:

message - the BigInteger message to encrypt or encrypt

Returns:

the encrypted or decrypted message

encode

protected byte[] encode()

Returns this RSA private key as DER encoded byte array (PKCS#1). The ASN.1 type is "RSAPrivateKey" and the coding is DER.

Overrides:

encode in class PrivateKeyInfo

Returns:

the RSA private key as a DER encoded ASN.1 datastructure

getPublicKey

public PublicKey getPublicKey()

Returns the public parts (modulus n and public exponent e of this private key.

Returns:

the public key part of this private key

getPrivateExponent

public java.math.BigInteger getPrivateExponent()

Returns the private exponent of this private key.

Returns:

the private exponent of the private key.

getPublicExponent

public java.math.BigInteger getPublicExponent()

Returns the public exponent of this private key.

Specified by:

getPublicExponent in interface RSAPrivateCrtKey

Returns:

the public exponent of the private key.

getModulus

public java.math.BigInteger getModulus()

Returns the modulus of this private key.

Returns:

the public modulus of the private key.

getPrimeP

public java.math.BigInteger getPrimeP()

Returns the first prime of this private key.

Specified by:

getPrimeP in interface RSAPrivateCrtKey

Returns:

the prime 1 of the private key.

getPrimeQ

public java.math.BigInteger getPrimeQ()

Returns the second prime of this private key.

Specified by:

getPrimeQ in interface RSAPrivateCrtKey

Returns:

the prime 2 of the private key.

getPrimeExponentP

public java.math.BigInteger getPrimeExponentP()

Returns the first exponent of this private key.

exponent = privateExponent mod (prime_p-1);

Specified by:

getPrimeExponentP in interface RSAPrivateCrtKey

Returns:

the exponent 1 of the private key.

getPrimeExponentQ

public java.math.BigInteger getPrimeExponentQ()

Returns the second exponent of this private key.

exponent = privateExponent mod (prime_q-1);

Specified by:

getPrimeExponentQ in interface RSAPrivateCrtKey

Returns:

the exponent 2 of the private key.

getCrtCoefficient

public java.math.BigInteger getCrtCoefficient()

Returns the Chinese Remainder Theorem coefficient of this private key.

crtCoefficient = multiplic inverse of prime_p mod prime_q;

Specified by:

getCrtCoefficient in interface RSAPrivateCrtKey

Returns:

the Chinese Remainder Theorem coefficient of the private key.

getAlgorithm

public java.lang.String getAlgorithm()

Returns the name of the appertaining algorithm.

Overrides:

getAlgorithm in class PrivateKeyInfo

Returns:

the string "RSA"

hashCode

public int hashCode()

Returns a hash code for this object.

Overrides:

hashCode in class java.lang.Object

Returns:

the hash code

toString

public java.lang.String toString()

Returns a string that represents the contents of this private key.

Overrides:

toString in class PrivateKeyInfo

Returns:

the string representation

clone

public java.lang.Object clone()

Overrides:

clone in class java.lang.Object