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gnu.java.security.sig.rsa
Class EMSA_PSS  

java.lang.Object
  gnu.java.security.sig.rsa.EMSA_PSS

All Implemented Interfaces:

java.lang.Cloneable

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public class EMSA_PSS

extends java.lang.Object

implements java.lang.Cloneable

An implementation of the EMSA-PSS encoding/decoding scheme.

EMSA-PSS coincides with EMSA4 in IEEE P1363a D5 except that EMSA-PSS acts on octet strings and not on bit strings. In particular, the bit lengths of the hash and the salt must be multiples of 8 in EMSA-PSS. Moreover, EMSA4 outputs an integer of a desired bit length rather than an octet string.

EMSA-PSS is parameterized by the choice of hash function Hash and mask generation function MGF. In this submission, MGF is based on a Hash definition that coincides with the corresponding definitions in IEEE Std 1363-2000, PKCS #1 v2.0, and the draft ANSI X9.44. In PKCS #1 v2.0 and the draft ANSI X9.44, the recommended hash function is SHA-1, while IEEE Std 1363-2000 recommends SHA-1 and RIPEMD-160.

References:

1. RSA-PSS Signature Scheme with Appendix, part B.
   Primitive specification and supporting documentation.
   Jakob Jonsson and Burt Kaliski.

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Field Summary
private static boolean	DEBUG
private static int	debuglevel
private static java.io.PrintWriter	err
private  gnu.java.security.hash.IMessageDigest	hash           The underlying hash function to use with this instance.
private  int	hLen           The output size of the hash function in octets.
private static java.lang.String	NAME

 

Constructor Summary
private	EMSA_PSS(gnu.java.security.hash.IMessageDigest hash)           Trivial private constructor to enforce use through Factory method.

 

Method Summary
java.lang.Object	clone()           This method may be called to create a new copy of the Object.
private static void	debug(java.lang.String s)
boolean	decode(byte[] mHash, byte[] EM, int emBits, int sLen)           The decoding operation EMSA-PSS-Decode recovers the message hash from an encoded message EM and compares it to the hash of M.
byte[]	encode(byte[] mHash, int emBits, byte[] salt)           The encoding operation EMSA-PSS-Encode computes the hash of a message M using a hash function and maps the result to an encoded message EM of a specified length using a mask generation function.
static EMSA_PSS	getInstance(java.lang.String mdName)           Returns an instance of this object given a designated name of a hash function.
private  byte[]	MGF(byte[] Z, int l)           A mask generation function takes an octet string of variable length and a desired output length as input, and outputs an octet string of the desired length.

 

Methods inherited from class java.lang.Object

equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

 

Field Detail

NAME

private static final java.lang.String NAME

See Also:

Constant Field Values

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DEBUG

private static final boolean DEBUG

See Also:

Constant Field Values

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debuglevel

private static final int debuglevel

See Also:

Constant Field Values

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err

private static final java.io.PrintWriter err

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hash

private gnu.java.security.hash.IMessageDigest hash

The underlying hash function to use with this instance.

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hLen

private int hLen

The output size of the hash function in octets.

Constructor Detail

EMSA_PSS

private EMSA_PSS(gnu.java.security.hash.IMessageDigest hash)

Trivial private constructor to enforce use through Factory method.

Method Detail

debug

private static void debug(java.lang.String s)

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getInstance

public static EMSA_PSS getInstance(java.lang.String mdName)

Returns an instance of this object given a designated name of a hash function.

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clone

public java.lang.Object clone()

Description copied from class: java.lang.Object

This method may be called to create a new copy of the Object. The typical behavior is as follows:

• o == o.clone() is false
• o.getClass() == o.clone().getClass() is true
• o.equals(o) is true

However, these are not strict requirements, and may be violated if necessary. Of the three requirements, the last is the most commonly violated, particularly if the subclass does not override Object.equals(Object)>Object.equals(Object) 55 .

If the Object you call clone() on does not implement java.lang.Cloneable (which is a placeholder interface), then a CloneNotSupportedException is thrown. Notice that Object does not implement Cloneable; this method exists as a convenience for subclasses that do.

Object's implementation of clone allocates space for the new Object using the correct class, without calling any constructors, and then fills in all of the new field values with the old field values. Thus, it is a shallow copy. However, subclasses are permitted to make a deep copy.

All array types implement Cloneable, and override this method as follows (it should never fail):

 public Object clone()
 {
   try
     {
       super.clone();
     }
   catch (CloneNotSupportedException e)
     {
       throw new InternalError(e.getMessage());
     }
 }
 

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encode

public byte[] encode(byte[] mHash,
                     int emBits,
                     byte[] salt)

The encoding operation EMSA-PSS-Encode computes the hash of a message M using a hash function and maps the result to an encoded message EM of a specified length using a mask generation function.

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decode

public boolean decode(byte[] mHash,
                      byte[] EM,
                      int emBits,
                      int sLen)

The decoding operation EMSA-PSS-Decode recovers the message hash from an encoded message EM and compares it to the hash of M.

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MGF

private byte[] MGF(byte[] Z,
                   int l)

A mask generation function takes an octet string of variable length and a desired output length as input, and outputs an octet string of the desired length. There may be restrictions on the length of the input and output octet strings, but such bounds are generally very large. Mask generation functions are deterministic; the octet string output is completely determined by the input octet string. The output of a mask generation function should be pseudorandom, that is, it should be infeasible to predict, given one part of the output but not the input, another part of the output. The provable security of RSA-PSS relies on the random nature of the output of the mask generation function, which in turn relies on the random nature of the underlying hash function.

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Overview  Package   Class  Use  Deprecated  Index
Home >> All >> gnu >> java >> security >> sig >> [ rsa overview ]	PREV CLASS  NEXT CLASS
SUMMARY:  JAVADOC |  SOURCE |  DOWNLOAD | NESTED | FIELD | CONSTR | METHOD	DETAIL: FIELD | CONSTR | METHOD

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