Package com.nettgryppa.security

Class HashCash

java.lang.Object

com.nettgryppa.security.HashCash

All Implemented Interfaces:

Comparable<HashCash>

public class HashCash
extends Object
implements Comparable<HashCash>

Class for generation and parsing of HashCash
Copyright 2006 Gregory Rubin grrubin@gmail.com
Permission is given to use, modify, and or distribute this code so long as this message remains attached
Please see the spec at: http://www.hashcash.org/

Version:

1.1

Author:

grrubin@gmail.com

Field Summary

Fields

Modifier and Type	Field	Description
static int	DefaultVersion

Constructor Summary

Constructors

Constructor	Description
HashCash(String cash)	Parses and validates a HashCash.

Method Summary

Modifier and Type	Method	Description
int	compareTo(HashCash other)	Compares the value of two HashCashes
boolean	equals(Object obj)	Two objects are considered equal if they are both of type HashCash and have an identical string representation
static long	estimateTime(int value)	Estimates how many milliseconds it would take to mint a cash of the specified value.
static int	estimateValue(int secs)	Estimates what value (e.g.
Calendar	getDate()	The minting date
Map<String,List<String>>	getExtensions()	Extra data encoded in the HashCash
String	getResource()	The primary resource being protected
int	getValue()	The value of the HashCash (e.g.
int	getVersion()	Which version of HashCash is used here
int	hashCode()	Implemented based on definition of equals()
static HashCash	mintCash(String resource, int value)	Mints a version 1 HashCash using now as the date
static HashCash	mintCash(String resource, int value, int version)	Mints a HashCash using now as the date
static HashCash	mintCash(String resource, Calendar date, int value)	Mints a version 1 HashCash
static HashCash	mintCash(String resource, Calendar date, int value, int version)	Mints a HashCash
static HashCash	mintCash(String resource, Map<String,List<String>> extensions, int value)	Mints a version 1 HashCash using now as the date
static HashCash	mintCash(String resource, Map<String,List<String>> extensions, int value, int version)	Mints a HashCash using now as the date
static HashCash	mintCash(String resource, Map<String,List<String>> extensions, Calendar date, int value)	Mints a version 1 HashCash
static HashCash	mintCash(String resource, Map<String,List<String>> extensions, Calendar date, int value, int version)	Mints a HashCash
String	toString()	Returns the canonical string representation of the HashCash

Methods inherited from class java.lang.Object

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

Field Detail

DefaultVersion

public static final int DefaultVersion

See Also:

Constant Field Values

Constructor Detail

HashCash

public HashCash(String cash)
         throws NoSuchAlgorithmException

Parses and validates a HashCash.

Throws:

NoSuchAlgorithmException - If SHA1 is not a supported Message Digest

Method Detail

mintCash

public static HashCash mintCash(String resource,
                                int value)
                         throws NoSuchAlgorithmException

Mints a version 1 HashCash using now as the date

Parameters:

resource - the string to be encoded in the HashCash

Throws:

NoSuchAlgorithmException - If SHA1 is not a supported Message Digest

mintCash

public static HashCash mintCash(String resource,
                                int value,
                                int version)
                         throws NoSuchAlgorithmException

Mints a HashCash using now as the date

Parameters:

resource - the string to be encoded in the HashCash

version - Which version to mint. Only valid values are 0 and 1

Throws:

NoSuchAlgorithmException - If SHA1 is not a supported Message Digest

mintCash

public static HashCash mintCash(String resource,
                                Calendar date,
                                int value)
                         throws NoSuchAlgorithmException

Mints a version 1 HashCash

Parameters:

resource - the string to be encoded in the HashCash

Throws:

NoSuchAlgorithmException - If SHA1 is not a supported Message Digest

mintCash

public static HashCash mintCash(String resource,
                                Calendar date,
                                int value,
                                int version)
                         throws NoSuchAlgorithmException

Mints a HashCash

Parameters:

resource - the string to be encoded in the HashCash

version - Which version to mint. Only valid values are 0 and 1

Throws:

NoSuchAlgorithmException - If SHA1 is not a supported Message Digest

mintCash

public static HashCash mintCash(String resource,
                                Map<String,List<String>> extensions,
                                int value)
                         throws NoSuchAlgorithmException

Mints a version 1 HashCash using now as the date

Parameters:

resource - the string to be encoded in the HashCash

extensions - Extra data to be encoded in the HashCash

Throws:

NoSuchAlgorithmException - If SHA1 is not a supported Message Digest

mintCash

public static HashCash mintCash(String resource,
                                Map<String,List<String>> extensions,
                                int value,
                                int version)
                         throws NoSuchAlgorithmException

Mints a HashCash using now as the date

Parameters:

resource - the string to be encoded in the HashCash

extensions - Extra data to be encoded in the HashCash

version - Which version to mint. Only valid values are 0 and 1

Throws:

NoSuchAlgorithmException - If SHA1 is not a supported Message Digest

mintCash

public static HashCash mintCash(String resource,
                                Map<String,List<String>> extensions,
                                Calendar date,
                                int value)
                         throws NoSuchAlgorithmException

Mints a version 1 HashCash

Parameters:

resource - the string to be encoded in the HashCash

extensions - Extra data to be encoded in the HashCash

Throws:

NoSuchAlgorithmException - If SHA1 is not a supported Message Digest

mintCash

public static HashCash mintCash(String resource,
                                Map<String,List<String>> extensions,
                                Calendar date,
                                int value,
                                int version)
                         throws NoSuchAlgorithmException

Mints a HashCash

Parameters:

resource - the string to be encoded in the HashCash

extensions - Extra data to be encoded in the HashCash

version - Which version to mint. Only valid values are 0 and 1

Throws:

NoSuchAlgorithmException - If SHA1 is not a supported Message Digest

equals

public boolean equals(Object obj)

Two objects are considered equal if they are both of type HashCash and have an identical string representation

Overrides:

equals in class Object

hashCode

public int hashCode()

Implemented based on definition of equals()

Overrides:

hashCode in class Object

toString

public String toString()

Returns the canonical string representation of the HashCash

Overrides:

toString in class Object

getExtensions

public Map<String,List<String>> getExtensions()

Extra data encoded in the HashCash

getResource

public String getResource()

The primary resource being protected

getDate

public Calendar getDate()

The minting date

getValue

public int getValue()

The value of the HashCash (e.g. how many leading zero bits it has)

getVersion

public int getVersion()

Which version of HashCash is used here

estimateTime

public static long estimateTime(int value)
                         throws NoSuchAlgorithmException

Estimates how many milliseconds it would take to mint a cash of the specified value.

• NOTE1: Minting time can vary greatly in fact, half of the time it will take half as long)
• NOTE2: The first time that an estimation function is called it is expensive (on the order of seconds). After that, it is very quick.

Throws:

NoSuchAlgorithmException - If SHA1 is not a supported Message Digest

estimateValue

public static int estimateValue(int secs)
                         throws NoSuchAlgorithmException

Estimates what value (e.g. how many bits of collision) are required for the specified length of time.

• NOTE1: Minting time can vary greatly in fact, half of the time it will take half as long)
• NOTE2: The first time that an estimation function is called it is expensive (on the order of seconds). After that, it is very quick.

Throws:

NoSuchAlgorithmException - If SHA1 is not a supported Message Digest

compareTo

public int compareTo(HashCash other)

Compares the value of two HashCashes

Specified by:

compareTo in interface Comparable<HashCash>

Parameters:

other -

See Also:

Comparable.compareTo(Object)