Interface for the data processing portion of stream ciphers. More...

#include <cryptlib.h>

Inheritance diagram for StreamTransformation:

Public Member Functions
StreamTransformation &	Ref ()
	Provides a reference to this object.

virtual unsigned int	MandatoryBlockSize () const
	Provides the mandatory block size of the cipher.

virtual unsigned int	OptimalBlockSize () const
	Provides the input block size most efficient for this cipher.

virtual unsigned int	GetOptimalBlockSizeUsed () const
	Provides the number of bytes used in the current block when processing at optimal block size.

virtual unsigned int	OptimalDataAlignment () const
	Provides input and output data alignment for optimal performance.

virtual void	ProcessData (byte outString, const byte inString, size_t length)=0
	Encrypt or decrypt an array of bytes.

virtual size_t	ProcessLastBlock (byte outString, size_t outLength, const byte inString, size_t inLength)
	Encrypt or decrypt the last block of data.

virtual unsigned int	MinLastBlockSize () const
	Provides the size of the last block.

virtual bool	IsLastBlockSpecial () const
	Determines if the last block receives special processing.

void	ProcessString (byte *inoutString, size_t length)
	Encrypt or decrypt a string of bytes.

void	ProcessString (byte outString, const byte inString, size_t length)
	Encrypt or decrypt a string of bytes.

byte	ProcessByte (byte input)
	Encrypt or decrypt a byte.

virtual bool	IsRandomAccess () const =0
	Determines whether the cipher supports random access.

virtual void	Seek (lword pos)
	Seek to an absolute position.

virtual bool	IsSelfInverting () const =0
	Determines whether the cipher is self-inverting.

virtual bool	IsForwardTransformation () const =0
	Determines if the cipher is being operated in its forward direction.

Public Member Functions inherited from Algorithm
	Algorithm (bool checkSelfTestStatus=true)
	Interface for all crypto algorithms.

virtual std::string	AlgorithmName () const
	Provides the name of this algorithm.

virtual std::string	AlgorithmProvider () const
	Retrieve the provider of this algorithm.

Public Member Functions inherited from Clonable
virtual Clonable *	Clone () const
	Copies this object.

Detailed Description

Interface for the data processing portion of stream ciphers.

See also: StreamTransformationFilter()

Definition at line 950 of file cryptlib.h.

Constructor & Destructor Documentation

◆ ~StreamTransformation()

virtual StreamTransformation::~StreamTransformation ( )

inlinevirtual

Definition at line 953 of file cryptlib.h.

Member Function Documentation

◆ Ref()

StreamTransformation & StreamTransformation::Ref ( )

inline

Provides a reference to this object.

Returns: A reference to this object

Useful for passing a temporary object to a function that takes a non-const reference

Definition at line 958 of file cryptlib.h.

◆ MandatoryBlockSize()

virtual unsigned int StreamTransformation::MandatoryBlockSize ( ) const

inlinevirtual

Provides the mandatory block size of the cipher.

Returns: The block size of the cipher if input must be processed in blocks, 1 otherwise

Stream ciphers and some block ciphers modes of operation return 1. Modes that return 1 must be able to process a single byte at a time, like counter mode. If a mode of operation or block cipher cannot stream then it must not return 1.

When filters operate the mode or cipher, ProcessData will be called with a string of bytes that is determined by MandatoryBlockSize and OptimalBlockSize. When a policy is set, like 16-byte strings for a 16-byte block cipher, the filter will buffer bytes until the specified number of bytes is available to the object.

See also: ProcessData, ProcessLastBlock, MandatoryBlockSize, MinLastBlockSize, BlockPaddingSchemeDef, IsLastBlockSpecial

Reimplemented in BlockOrientedCipherModeBase.

Definition at line 970 of file cryptlib.h.

◆ OptimalBlockSize()

virtual unsigned int StreamTransformation::OptimalBlockSize ( ) const

inlinevirtual

Provides the input block size most efficient for this cipher.

Returns: The input block size that is most efficient for the cipher

The base class implementation returns MandatoryBlockSize().

Note: Optimal input length is n * OptimalBlockSize() - GetOptimalBlockSizeUsed() for any n > 0.

Reimplemented in ECB_OneWay, AdditiveCipherTemplate< AbstractPolicyHolder< AdditiveCipherAbstractPolicy, CTR_ModePolicy > >, and CFB_CipherTemplate< AbstractPolicyHolder< CFB_CipherAbstractPolicy, SymmetricCipher > >.

Definition at line 977 of file cryptlib.h.

◆ GetOptimalBlockSizeUsed()

virtual unsigned int StreamTransformation::GetOptimalBlockSizeUsed ( ) const

inlinevirtual

Provides the number of bytes used in the current block when processing at optimal block size.

Returns: the number of bytes used in the current block when processing at the optimal block size

Definition at line 981 of file cryptlib.h.

◆ OptimalDataAlignment()

virtual unsigned int StreamTransformation::OptimalDataAlignment ( ) const

virtual

Provides input and output data alignment for optimal performance.

Returns: the input data alignment that provides optimal performance

See also: GetAlignment() and OptimalBlockSize()

Reimplemented in CCM_Base, ChaCha20Poly1305_Base, XChaCha20Poly1305_Base, EAX_Base, GCM_Base, CipherModeBase, AdditiveCipherTemplate< AbstractPolicyHolder< AdditiveCipherAbstractPolicy, CTR_ModePolicy > >, CFB_CipherTemplate< AbstractPolicyHolder< CFB_CipherAbstractPolicy, SymmetricCipher > >, and XTS_ModeBase.

◆ ProcessData()

virtual void StreamTransformation::ProcessData	(	byte *	outString,
		const byte *	inString,
		size_t	length )

pure virtual

Encrypt or decrypt an array of bytes.

Parameters

outString	the output byte buffer
inString	the input byte buffer
length	the size of the input and output byte buffers, in bytes

ProcessData is called with a string of bytes whose size depends on MandatoryBlockSize. Either inString == outString, or they must not overlap.

See also: ProcessData, ProcessLastBlock, MandatoryBlockSize, MinLastBlockSize, BlockPaddingSchemeDef, IsLastBlockSpecial

Implemented in Weak::ARC4_Base, AuthenticatedSymmetricCipherBase, PublicBlumBlumShub, ECB_OneWay, CBC_Encryption, CBC_Decryption, AdditiveCipherTemplate< AbstractPolicyHolder< AdditiveCipherAbstractPolicy, CTR_ModePolicy > >, CFB_CipherTemplate< AbstractPolicyHolder< CFB_CipherAbstractPolicy, SymmetricCipher > >, and XTS_ModeBase.

◆ ProcessLastBlock()

virtual size_t StreamTransformation::ProcessLastBlock	(	byte *	outString,
		size_t	outLength,
		const byte *	inString,
		size_t	inLength )

virtual

Encrypt or decrypt the last block of data.

Parameters

outString	the output byte buffer
outLength	the size of the output byte buffer, in bytes
inString	the input byte buffer
inLength	the size of the input byte buffer, in bytes

Returns: the number of bytes used in outString

ProcessLastBlock is used when the last block of data is special and requires handling by the cipher. The current implementation provides an output buffer with a size inLength+2*MandatoryBlockSize(). The return value allows the cipher to expand cipher text during encryption or shrink plain text during decryption.

This member function is used by CBC-CTS and OCB modes.

See also: ProcessData, ProcessLastBlock, MandatoryBlockSize, MinLastBlockSize, BlockPaddingSchemeDef, IsLastBlockSpecial

Reimplemented in CBC_CTS_Encryption, CBC_CTS_Decryption, and XTS_ModeBase.

◆ MinLastBlockSize()

virtual unsigned int StreamTransformation::MinLastBlockSize ( ) const

inlinevirtual

Provides the size of the last block.

Returns: the minimum size of the last block

MinLastBlockSize() returns the minimum size of the last block. 0 indicates the last block is not special.

MandatoryBlockSize() enlists one of two behaviors. First, if MandatoryBlockSize() returns 1, then the cipher can be streamed and ProcessData() is called with the tail bytes. Second, if MandatoryBlockSize() returns non-0, then the string of bytes is padded to MandatoryBlockSize() according to the padding mode. Then, ProcessData() is called with the padded string of bytes.

Some authenticated encryption modes are not expressed well with MandatoryBlockSize() and MinLastBlockSize(). For example, AES/OCB uses 16-byte blocks (MandatoryBlockSize = 16) and the last block requires special processing (MinLastBlockSize = 0). However, 0 is a valid last block size for OCB and the special processing is custom padding, and not standard PKCS padding. In response an unambiguous IsLastBlockSpecial() was added.

See also: ProcessData, ProcessLastBlock, MandatoryBlockSize, MinLastBlockSize, BlockPaddingSchemeDef, IsLastBlockSpecial

Reimplemented in CBC_ModeBase, CBC_CTS_Encryption, CBC_CTS_Decryption, and XTS_ModeBase.

Definition at line 1026 of file cryptlib.h.

◆ IsLastBlockSpecial()

virtual bool StreamTransformation::IsLastBlockSpecial ( ) const

inlinevirtual

Determines if the last block receives special processing.

Returns: true if the last block receives special processing, false otherwise.

Some authenticated encryption modes are not expressed well with MandatoryBlockSize() and MinLastBlockSize(). For example, AES/OCB uses 16-byte blocks (MandatoryBlockSize = 16) and the last block requires special processing (MinLastBlockSize = 0). However, 0 is a valid last block size for OCB and the special processing is custom padding, and not standard PKCS padding. In response an unambiguous IsLastBlockSpecial() was added.

When IsLastBlockSpecial() returns false nothing special happens. All the former rules and behaviors apply. This is the default behavior of IsLastBlockSpecial().

When IsLastBlockSpecial() returns true four things happen. First, MinLastBlockSize = 0 means 0 is a valid block size that should be processed. Second, standard block cipher padding is not applied. Third, the caller supplies an outString is larger than inString by 2*MandatoryBlockSize(). That is, there's a reserve available when processing the last block. Fourth, the cipher is responsible for finalization like custom padding. The cipher will tell the library how many bytes were processed or used by returning the appropriate value from ProcessLastBlock().

The return value of ProcessLastBlock() indicates how many bytes were written to outString. A filter pipelining data will send outString and up to outLength to an AttachedTransformation() for additional processing. Below is an example of the code used in StreamTransformationFilter::LastPut.

  if (m_cipher.IsLastBlockSpecial())
  {
    size_t reserve = 2*m_cipher.MandatoryBlockSize();
    space = HelpCreatePutSpace(*AttachedTransformation(), DEFAULT_CHANNEL, length+reserve);
    length = m_cipher.ProcessLastBlock(space, length+reserve, inString, length);
    AttachedTransformation()->Put(space, length);
    return;
  }

See also: ProcessData, ProcessLastBlock, MandatoryBlockSize, MinLastBlockSize, BlockPaddingSchemeDef, IsLastBlockSpecial

Since: Crypto++ 6.0

Definition at line 1059 of file cryptlib.h.

◆ ProcessString() [1/2]

void StreamTransformation::ProcessString	(	byte *	inoutString,
		size_t	length )

inline

Encrypt or decrypt a string of bytes.

Parameters

inoutString	the string to process
length	the size of the inoutString, in bytes

Internally, the base class implementation calls ProcessData().

Definition at line 1065 of file cryptlib.h.

◆ ProcessString() [2/2]

void StreamTransformation::ProcessString	(	byte *	outString,
		const byte *	inString,
		size_t	length )

inline

Encrypt or decrypt a string of bytes.

Parameters

outString	the output string to process
inString	the input string to process
length	the size of the input and output strings, in bytes

Internally, the base class implementation calls ProcessData().

Definition at line 1073 of file cryptlib.h.

◆ ProcessByte()

byte StreamTransformation::ProcessByte ( byte input )

inline

Encrypt or decrypt a byte.

Parameters

input the input byte to process

Internally, the base class implementation calls ProcessData() with a size of 1.

Definition at line 1079 of file cryptlib.h.

◆ IsRandomAccess()

virtual bool StreamTransformation::IsRandomAccess ( ) const

pure virtual

Determines whether the cipher supports random access.

Returns: true if the cipher supports random access, false otherwise

Implemented in Weak::ARC4_Base, AuthenticatedSymmetricCipherBase, BlumBlumShub, BlockOrientedCipherModeBase, AdditiveCipherTemplate< AbstractPolicyHolder< AdditiveCipherAbstractPolicy, CTR_ModePolicy > >, and CFB_CipherTemplate< AbstractPolicyHolder< CFB_CipherAbstractPolicy, SymmetricCipher > >.

◆ Seek()

virtual void StreamTransformation::Seek ( lword pos )

inlinevirtual

Seek to an absolute position.

Parameters

pos	position to seek

Exceptions

NotImplemented

The base class implementation throws NotImplemented. The function asserts IsRandomAccess() in debug builds.

Reimplemented in BlumBlumShub, and AdditiveCipherTemplate< AbstractPolicyHolder< AdditiveCipherAbstractPolicy, CTR_ModePolicy > >.

Definition at line 1091 of file cryptlib.h.

◆ IsSelfInverting()

virtual bool StreamTransformation::IsSelfInverting ( ) const

pure virtual

Determines whether the cipher is self-inverting.

Returns: true if the cipher is self-inverting, false otherwise

IsSelfInverting determines whether this transformation is self-inverting (e.g. xor with a keystream).

Implemented in Weak::ARC4_Base, AuthenticatedSymmetricCipherBase, PublicBlumBlumShub, BlockOrientedCipherModeBase, AdditiveCipherTemplate< AbstractPolicyHolder< AdditiveCipherAbstractPolicy, CTR_ModePolicy > >, and CFB_CipherTemplate< AbstractPolicyHolder< CFB_CipherAbstractPolicy, SymmetricCipher > >.

◆ IsForwardTransformation()

virtual bool StreamTransformation::IsForwardTransformation ( ) const

pure virtual

Determines if the cipher is being operated in its forward direction.

Returns: true if DIR is ENCRYPTION, false otherwise

See also: IsForwardTransformation(), IsPermutation(), GetCipherDirection()

Implemented in Weak::ARC4_Base, PublicBlumBlumShub, CCM_Final< T_BlockCipher, T_DefaultDigestSize, T_IsEncryption >, EAX_Final< T_BlockCipher, T_IsEncryption >, GCM_Final< T_BlockCipher, T_TablesOption, T_IsEncryption >, BlockOrientedCipherModeBase, and AdditiveCipherTemplate< AbstractPolicyHolder< AdditiveCipherAbstractPolicy, CTR_ModePolicy > >.

The documentation for this class was generated from the following file:

cryptlib.h

Public Member Functions

Detailed Description

Constructor & Destructor Documentation

◆ ~StreamTransformation()

Member Function Documentation

◆ Ref()

◆ MandatoryBlockSize()

◆ OptimalBlockSize()

◆ GetOptimalBlockSizeUsed()

◆ OptimalDataAlignment()

◆ ProcessData()

◆ ProcessLastBlock()

◆ MinLastBlockSize()

◆ IsLastBlockSpecial()

◆ ProcessString() [1/2]

◆ ProcessString() [2/2]

◆ ProcessByte()

◆ IsRandomAccess()

◆ Seek()

◆ IsSelfInverting()

◆ IsForwardTransformation()