Class: HashStream

• Inheritance
• Description
• Class protocol
  • Compatibility-Squeak
  • instance creation
  • queries
  • self tests
  • utilities
• Instance protocol
  • Compatibility-Squeak
  • accessing
  • not implemented
  • operations
  • queries
  • writing
• Examples

Inheritance:

   Object
   |
   +--Stream
      |
      +--HashStream
         |
         +--CRCStream
         |
         +--MD5Stream
         |
         +--SHA1Stream

Package:

stx:libbasic

Category:

System-Crypt-Hashing

Version:

rev: 1.50 date: 2024/01/30 09:35:57

user: cg

file: HashStream.st directory: libbasic

module: stx stc-classLibrary: libbasic

Description:

Abstract class.
Subclasses generate hash values used as checksums
or for generating cryptographic signatures.

Notice: due to historic reasons and compatibility with Squeak,
there are two modes of operation:
    1) hashFunction mode, in which the hash of a single block of bytes is computed
    2) hashStream mode, in which instances behave like a writeStream, computing and
       updating the hash, as data is sent to it.

hashFunction mode is called using: #hashValueOf:aStringOrByteArray
Warning: Not all subclasses support the stream mode
         (especially those which were ported from squeak do not).

copyright
COPYRIGHT (c) 1999 by eXept Software AG
             All Rights Reserved

This software is furnished under a license and may be used
only in accordance with the terms of that license and with the
inclusion of the above copyright notice.   This software may not
be provided or otherwise made available to, or used by, any
other person.  No title to or ownership of the software is
hereby transferred.

Class protocol:

 hashMessage: aStringOrByteArrayOrStream

SQUEAK compatibility
- but this is a bad choice - squeak uses #digestMessage: at the instance side

 new

have to re-allow new - it was disabled in Stream

 random

create a random number generator using myself

Usage example(s):

SHA1Stream random next

 blockSize

return the block size (in bytes) when the hash is used by encryption/decryption.
(see OfbCipherMode and CtrCipherMode)

 canStream

simple hash functions (squeak-ported) cannot stream.
Use hashFunction: there

 hashBlockSize

return the block size used internally by the compression function

** This method must be redefined in concrete classes (subclassResponsibility) **

 hashSize

return the size of the hashvalue returned by instances of this class (in bytes)

** This method must be redefined in concrete classes (subclassResponsibility) **

 isAbstract

Return if this class is an abstract class.
True is returned here for myself only; false for subclasses.
Abstract subclasses must redefine this again.

 test

test against testVector

Usage example(s):

MD5Stream test. SHA1Stream test. RipeMD160Stream test.

 testVector

obsolete - moved to TestHashAlgorithms unit test.

** This method must be redefined in concrete classes (subclassResponsibility) **

 cryptBlock: aStringOrByteArray from: srcIdx to: srcEndOrNil into: resultOrNil startingAt: dstIdx encrypt: encryptMode

one-way encryption of aStringOrByteArray.
Used when a HashStream is used as the block cipher with OFB or CTR mode.

encryptMode is ignored here.

 digestMessage: aStringOrByteArrayOrStream

 hashValueHexString: aString

MD5Stream hashValueHexString:'abc'
MD5Stream hashValueHexString:'Hello World'
MD5Stream hashValueOf:'Hello World'

 hashValueOf: aStringOrByteArrayOrStream

MD5Stream hashValueOf:'BlaBlaBla'
MD5Stream hashValueOf:('makefile' asFilename readStream)
MD5Stream hashValueOf:('BlaBlaBla' readStream)

 hashValueOfFile: aFilename

generate a hashValue for the whole contents of a file

Usage example(s):

MD5Stream hashValueOfFile:'makefile'

Instance protocol:

 digestMessage: bytes

SQUEAK: answer the digest of bytes

 hashMessage: bytes

SQUEAK: answer the digest of bytes

 contents

return the entire contents of the stream
- this is our hashValue.

 next

I can only write

 hashValueOf: bytes

answer the digest of bytes

Usage example(s):

SHA1Stream new hashValueOf:'123456789abcdefg'; hashValueOf:'123456789abcdefg' (SHA1Stream new hmac key:'123456') hashValueOf:'123456789abcdefg'; hashValueOf:'123456789abcdefg' (SHA1Stream new hmac key:'123456') nextPutAll:'123456789abcdefg'; contents

 reset

initialize to a clean state

** This method must be redefined in concrete classes (subclassResponsibility) **

 atEnd

return true if the end of the stream has been reached;
this is never reached

 blockSize

the class knows about the basic block size (in bytes)

 canStream

 hashBlockSize

the class knows about the basic block size

 hashSize

return the size of the returned hashvalue (in bytes)

 hashValue

return the value of the computed hash

** This method must be redefined in concrete classes (subclassResponsibility) **

 isReadable

return true, if reading is supported by the receiver.
Always return false here

 isWritable

return true, if writing is supported by the receiver.
Always return true here

 nextPut: anObject

add the hash of anObject to the computed hash so far.
anObject can be a Character, SmallInteger ByteArray or String.
Answer the argument

 nextPutAll: aCollection

Hash streams handle Strings and ByteArrays in #nextPutBytes:
Answer the receiver

 nextPutAll: count from: aCollection startingAt: initialIndex

Hash streams handle Strings and ByteArrays in #nextPutBytes:
Answer the number of elements written

 nextPutByte: aByte

add the hash of anObject to the computed hash so far.
aByte can be a SmallInteger <= 255

 nextPutBytes: count from: anObject startingAt: start

write count bytes from an object starting at index start.
Return the number of bytes written.
The object must have non-pointer indexed instvars
(i.e. be a ByteArray, String, Float- or DoubleArray).

** This method must be redefined in concrete classes (subclassResponsibility) **

Examples:

  MD5Stream hashValueOf:'hello world'
  MD4Stream hashValueOf:'hello world'

  |md5|

  md5 := MD5Stream new.
  md5 nextPutAll:'hello world'.
  md5 hashValue