RSAPublicKey ("Entrust Authority Security Toolkit for the Java Platform")

java.lang.Object
- iaik.x509.PublicKeyInfo
- - iaik.security.rsa.RSAPublicKey

All Implemented Interfaces:

ASN1Type, java.io.Serializable, java.lang.Cloneable, java.security.interfaces.RSAKey, java.security.interfaces.RSAPublicKey, java.security.Key, java.security.PublicKey
```
public class RSAPublicKey
extends PublicKeyInfo
implements java.security.interfaces.RSAPublicKey, java.io.Serializable, java.lang.Cloneable
```
This class implements a RSA public key and supports ASN.1 encoding. This class extends iaik.x509.PublicKeyInfo for supporting RSA public keys to be used within X.509 certificates. This class implements the java.security.interfaces.RSAPublicKey interface for providing the functionality of a public key, as used for data encrypting or signature verifying based on the RSA algorithm.
PKCS #1: RSA Encryption Version 1.5 (RFC 2313) describes a X.509/PEM compatible syntax for RSA public keys to be used in certificates. The corresponding ASN.1 type RSAPublicKey is defined as ASN.1 SEQUENCE:
```
 RSAPublicKey ::= SEQUENCE {
   modulus INTEGER, -- n
   publicExponent INTEGER -- e }
 
```
An application wishing to create a RSAPublicKey to be used for, e.g. data encryption or signature verifying 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 RSAPublicKey by using a proper KeyPairGenerator:
- First the KeyPairGenerator has to be instantiated thereby specifying the application's 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 public key, it has to be obtained from the key pair just created:
```
 RSAPublicKey rsa_pub_key = (RSAPublicKey)key_pair.getPublic();
 
```
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:

PublicKeyInfo, RSAPublicKey, KeyPairGenerator, KeyPair, RsaCipher, RSAKey, RSAPrivateKey, RSAKeyPairGenerator, RSAKeyFactory, Serialized Form

Field Summary
- Fields inherited from class iaik.x509.PublicKeyInfo
  public_key_algorithm
- Fields inherited from interface java.security.interfaces.RSAPublicKey
  serialVersionUID

Constructor Summary

Constructors
Constructor and Description
`RSAPublicKey(ASN1Object obj)` Creates a new RSAPublicKey from the given ASN.1 object.
`RSAPublicKey(java.math.BigInteger modulus, java.math.BigInteger publicExponent)` Creates a new RSAPublicKey with given values for the modulus `n` and the public exponent `e`.
`RSAPublicKey(byte[] pk)` Creates a new RSAPublicKey from the given DER encoded byte array.
`RSAPublicKey(java.io.InputStream is)` Creates a new RSAPublicKey from an InputStream.
`RSAPublicKey(java.security.interfaces.RSAPublicKey key)` Creates a new RSAPublicKey from the given RSAPublicKey representing modulus `n` and public exponent `e`.
`RSAPublicKey(java.security.spec.RSAPublicKeySpec keySpec)` Creates a new RSAPublicKey from the given RSAPublicKeySpec representing modulus `n` and public exponent `e`.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`java.lang.Object`	`clone()` Returns a clone of this RSAPublicKey object.
`java.math.BigInteger`	`crypt(java.math.BigInteger message)` Uses the public key to encrypt or decrypt a message.
`protected void`	`decode(byte[] publicKey)` Decodes a RSAPublicKey, encoded in DER format (PKCS#1).
`protected byte[]`	`encode()` Returns this RSA public key as DER encoded ASN.1 object (PKCS#1).
`boolean`	`equals(java.lang.Object obj)` Compares this RSAPublicKey object with the supplied object.
`java.lang.String`	`getAlgorithm()` Returns the name of the appertaining algorithm.
`byte[]`	`getFingerprint()` Returns the fingerprint of this RSA public key.
`java.math.BigInteger`	`getModulus()` Returns the modulus of the public key.
`java.math.BigInteger`	`getPublicExponent()` Returns the public exponent of the public key.
`int`	`hashCode()` Returns a hash code for this object.
`java.lang.String`	`toString()` Returns a string that represents the contents of this RSA public key.

Methods inherited from class iaik.x509.PublicKeyInfo
createPublicKeyInfo, decode, getEncoded, getFormat, getPublicKey, getPublicKey, toASN1Object, writeTo

Methods inherited from class java.lang.Object
finalize, getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.security.Key
getEncoded, getFormat

Methods inherited from interface java.security.interfaces.RSAKey
getParams

- Constructor Detail
  - RSAPublicKey
```
public RSAPublicKey(java.math.BigInteger modulus,
                    java.math.BigInteger publicExponent)
```
    Creates a new RSAPublicKey with given values for the modulus n and the public exponent e.
    
    Parameters:
    
    modulus - the modulus of the key
    
    publicExponent - the public exponent of the key
  - RSAPublicKey
```
public RSAPublicKey(java.security.spec.RSAPublicKeySpec keySpec)
```
    Creates a new RSAPublicKey from the given RSAPublicKeySpec representing modulus n and public exponent e.
    
    Parameters:
    
    keySpec - the RSAPublicKeySpec representing modulus n and public exponent e
  - RSAPublicKey
```
public RSAPublicKey(java.security.interfaces.RSAPublicKey key)
```
    Creates a new RSAPublicKey from the given RSAPublicKey representing modulus n and public exponent e.
    
    Parameters:
    
    key - the RSAPublicKey representing modulus n and public exponent e
  - RSAPublicKey
```
public RSAPublicKey(byte[] pk)
             throws java.security.InvalidKeyException
```
    Creates a new RSAPublicKey from the given DER encoded byte array.
    This constructor may be used for parsing an already exisiting RSA public key, wrapped into a X.509 PublicKeyInfo that is supplied as DER encoded byte array.
    
    Parameters:
    
    pk - the byte array holding the DER encoded public key info
    
    Throws:
    
    java.security.InvalidKeyException - if something is wrong with the key encoding
  - RSAPublicKey
```
public RSAPublicKey(ASN1Object obj)
             throws java.security.InvalidKeyException
```
    Creates a new RSAPublicKey from the given ASN.1 object. The supplied ASN1Object represents a X.509 PublicKeyInfo holding the RSA public key.
    
    Parameters:
    
    obj - the public key ASN.1 structure
    
    Throws:
    
    java.security.InvalidKeyException - if something is wrong with the key encoding
  - RSAPublicKey
```
public RSAPublicKey(java.io.InputStream is)
             throws java.io.IOException,
                    java.security.InvalidKeyException
```
    Creates a new RSAPublicKey from an InputStream.
    This constructor may be used for parsing an already exisiting RSA public key, wrapped into a X.509 PublicKeyInfo that is supplied as DER encoded byte array.
    
    Parameters:
    
    is - an input stream with the data to be read to initialize the public key
    
    Throws:
    
    java.io.IOException - if an I/O error occurs
    
    java.security.InvalidKeyException - if something is wrong with the key encoding
- Method Detail
  - decode
```
protected void decode(byte[] publicKey)
               throws java.security.InvalidKeyException
```
    Decodes a RSAPublicKey, encoded in DER format (PKCS#1).
    From the given DER encoded byte array an ASN.1 object is created and parsed for modulus n and public exponent e.
    This method is protected and typically will not be used by an application. Rather it is used by the parent X.509 PublicKeyInfo class for decoding the inherent RSA public key.
    
    Specified by:
    
    decode in class PublicKeyInfo
    
    Parameters:
    
    publicKey - the public key as DER encoded ASN.1 object (PKCS#1)
    
    Throws:
    
    java.security.InvalidKeyException - if something is wrong with the encoding of the key
  - encode
```
protected byte[] encode()
```
    Returns this RSA public key as DER encoded ASN.1 object (PKCS#1).
    This method is protected and typically will not be used by an application. Rather it is used by the parent X.509 PublicKeyInfo class for encoding the inherent RSA public key.
    
    Specified by:
    
    encode in class PublicKeyInfo
    
    Returns:
    
    a byte array holding the RSA public key as a DER encoded ASN.1 datastructure (PKCS#1)
  - crypt
```
public java.math.BigInteger crypt(java.math.BigInteger message)
```
    Uses the public key to encrypt or decrypt a message. Simply performs a modulo exponentiation.
    
    Parameters:
    
    message - the message to en/decrypt as BigInteger
    
    Returns:
    
    the encrypted or decrypted message
  - getAlgorithm
```
public java.lang.String getAlgorithm()
```
    Returns the name of the appertaining algorithm.
    
    Specified by:
    
    getAlgorithm in interface java.security.Key
    
    Specified by:
    
    getAlgorithm in class PublicKeyInfo
    
    Returns:
    
    the string "RSA"
  - getPublicExponent
```
public java.math.BigInteger getPublicExponent()
```
    Returns the public exponent of the public key.
    
    Specified by:
    
    getPublicExponent in interface java.security.interfaces.RSAPublicKey
    
    Returns:
    
    the public exponent
  - getModulus
```
public java.math.BigInteger getModulus()
```
    Returns the modulus of the public key.
    
    Specified by:
    
    getModulus in interface java.security.interfaces.RSAKey
    
    Returns:
    
    the modulus
  - getFingerprint
```
public byte[] getFingerprint()
```
    Returns the fingerprint of this RSA public key. This is a MD5 hash of the DER encoded SubjectPublicKey.
    
    Overrides:
    
    getFingerprint in class PublicKeyInfo
    
    Returns:
    
    the fingerprint of this RSA public key
  - 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 RSA public key.
    
    Overrides:
    
    toString in class PublicKeyInfo
    
    Returns:
    
    the string representation
  - equals
```
public boolean equals(java.lang.Object obj)
```
    Compares this RSAPublicKey object with the supplied object.
    
    Overrides:
    
    equals in class PublicKeyInfo
    
    Parameters:
    
    obj - the object to be compared
    
    Returns:
    
    true if the two objects are RSAPublicKey objects with same modulus and exponent, false otherwise
  - clone
```
public java.lang.Object clone()
```
    Returns a clone of this RSAPublicKey object.
    
    Overrides:
    
    clone in class java.lang.Object
    
    Returns:
    
    a clone of this object

Class RSAPublicKey

Field Summary

Fields inherited from class iaik.x509.PublicKeyInfo

Fields inherited from interface java.security.interfaces.RSAPublicKey

Constructor Summary

Method Summary

Methods inherited from class iaik.x509.PublicKeyInfo

Methods inherited from class java.lang.Object

Methods inherited from interface java.security.Key

Methods inherited from interface java.security.interfaces.RSAKey

Constructor Detail

RSAPublicKey

RSAPublicKey

RSAPublicKey

RSAPublicKey

RSAPublicKey

RSAPublicKey

Method Detail

decode

encode

crypt

getAlgorithm

getPublicExponent

getModulus

getFingerprint

hashCode

toString

equals

clone