# SymmetricCipher Class Reference

`#include <cryptlib.h>`

Inheritance diagram for SymmetricCipher:

List of all members.

## Detailed Description

interface for one direction (encryption or decryption) of a stream cipher or cipher mode

Definition at line 622 of file cryptlib.h.

## Public Types
enum | IV_Requirement { UNIQUE_IV = 0, RANDOM_IV, UNPREDICTABLE_RANDOM_IV, INTERNALLY_GENERATED_IV, NOT_RESYNCHRONIZABLE }
## Public Member Functions
virtual size_t | MinKeyLength () const =0
| returns smallest valid key length in bytes */
virtual size_t | MaxKeyLength () const =0
| returns largest valid key length in bytes */
virtual size_t | DefaultKeyLength () const =0
| returns default (recommended) key length in bytes */
virtual size_t | GetValidKeyLength (size_t n) const =0
| returns the smallest valid key length in bytes that is >= min(n, GetMaxKeyLength())
virtual bool | IsValidKeyLength (size_t n) const
| returns whether n is a valid key length
virtual void | SetKey (const byte *key, size_t length, const NameValuePairs &params=g_nullNameValuePairs)
| set or reset the key of this object
void | SetKeyWithRounds (const byte *key, size_t length, int rounds)
| calls SetKey() with an NameValuePairs object that just specifies "Rounds"
void | SetKeyWithIV (const byte *key, size_t length, const byte *iv, size_t ivLength)
| calls SetKey() with an NameValuePairs object that just specifies "IV"
void | SetKeyWithIV (const byte *key, size_t length, const byte *iv)
| calls SetKey() with an NameValuePairs object that just specifies "IV"
virtual IV_Requirement | IVRequirement () const =0
| returns the minimal requirement for secure IVs
bool | IsResynchronizable () const
| returns whether this object can be resynchronized (i.e. supports initialization vectors)
bool | CanUseRandomIVs () const
| returns whether this object can use random IVs (in addition to ones returned by GetNextIV)
bool | CanUsePredictableIVs () const
| returns whether this object can use random but possibly predictable IVs (in addition to ones returned by GetNextIV)
bool | CanUseStructuredIVs () const
| returns whether this object can use structured IVs, for example a counter (in addition to ones returned by GetNextIV)
virtual unsigned int | IVSize () const
unsigned int | DefaultIVLength () const
| returns default length of IVs accepted by this object
virtual unsigned int | MinIVLength () const
| returns minimal length of IVs accepted by this object
virtual unsigned int | MaxIVLength () const
| returns maximal length of IVs accepted by this object
virtual void | Resynchronize (const byte *iv, int ivLength=-1)
| resynchronize with an IV. ivLength=-1 means use IVSize()
virtual void | GetNextIV (RandomNumberGenerator &rng, byte *IV)
| get a secure IV for the next message
StreamTransformation & | Ref ()
| return a reference to this object,
virtual unsigned int | MandatoryBlockSize () const
| returns block size, if input must be processed in blocks, otherwise 1
virtual unsigned int | OptimalBlockSize () const
| returns the input block size that is most efficient for this cipher
virtual unsigned int | GetOptimalBlockSizeUsed () const
| returns how much of the current block is used up
virtual unsigned int | OptimalDataAlignment () const
| returns how input should be aligned for optimal performance
virtual void | ProcessData (byte *outString, const byte *inString, size_t length)=0
| encrypt or decrypt an array of bytes of specified length
virtual void | ProcessLastBlock (byte *outString, const byte *inString, size_t length)
| for ciphers where the last block of data is special, encrypt or decrypt the last block of data
virtual unsigned int | MinLastBlockSize () const
| returns the minimum size of the last block, 0 indicating the last block is not special
void | ProcessString (byte *inoutString, size_t length)
| same as ProcessData(inoutString, inoutString, length)
void | ProcessString (byte *outString, const byte *inString, size_t length)
| same as ProcessData(outString, inString, length)
byte | ProcessByte (byte input)
| implemented as {ProcessData(&input, &input, 1); return input;}
virtual bool | IsRandomAccess () const =0
| returns whether this cipher supports random access
virtual void | Seek (lword n)
| for random access ciphers, seek to an absolute position
virtual bool | IsSelfInverting () const =0
| returns whether this transformation is self-inverting (e.g. xor with a keystream)
virtual bool | IsForwardTransformation () const =0
| returns whether this is an encryption object
virtual std::string | AlgorithmName () const
| returns name of this algorithm, not universally implemented yet
virtual Clonable * | Clone () const
| this is not implemented by most classes yet
## Protected Member Functions
const Algorithm & | GetAlgorithm () const
virtual void | UncheckedSetKey (const byte *key, unsigned int length, const NameValuePairs &params)=0
void | ThrowIfInvalidKeyLength (size_t length)
void | ThrowIfResynchronizable ()
void | ThrowIfInvalidIV (const byte *iv)
size_t | ThrowIfInvalidIVLength (int size)
const byte * | GetIVAndThrowIfInvalid (const NameValuePairs &params, size_t &size)
void | AssertValidKeyLength (size_t length) const

## Member Function Documentation

void SimpleKeyingInterface::SetKey | ( | const byte * | key,
|  | size_t | length,
|  | const NameValuePairs & | params = `g_nullNameValuePairs` |
| ) |  |  | `[virtual, inherited]`

set or reset the key of this object

Parameters:

  | params | is used to specify Rounds, BlockSize, etc.

Reimplemented in AuthenticatedSymmetricCipherBase.

Definition at line 53 of file cryptlib.cpp.

Referenced by SimpleKeyingInterface::SetKeyWithIV(), and SimpleKeyingInterface::SetKeyWithRounds().

bool SimpleKeyingInterface::IsResynchronizable | ( |  | ) | const`[inline, inherited]`

returns whether this object can be resynchronized (i.e. supports initialization vectors)

If this function returns true, and no IV is passed to SetKey() and CanUseStructuredIVs()==true, an IV of all 0's will be assumed.

Definition at line 393 of file cryptlib.h.

void SimpleKeyingInterface::GetNextIV | ( | RandomNumberGenerator & | rng,
|  | byte * | IV |
| ) |  |  | `[virtual, inherited]`

get a secure IV for the next message

This method should be called after you finish encrypting one message and are ready to start the next one. After calling it, you must call SetKey() or Resynchronize() before using this object again. This method is not implemented on decryption objects.

Definition at line 129 of file cryptlib.cpp.

References RandomNumberGenerator::GenerateBlock().

StreamTransformation& StreamTransformation::Ref | ( |  | ) | `[inline, inherited]`

return a reference to this object,

This function is useful for passing a temporary StreamTransformation object to a function that takes a non-const reference.

Definition at line 483 of file cryptlib.h.

virtual unsigned int StreamTransformation::OptimalBlockSize | ( |  | ) | const`[inline, virtual, inherited]`

returns the input block size that is most efficient for this cipher

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

Definition at line 490 of file cryptlib.h.

virtual void StreamTransformation::ProcessData | ( | byte * | outString,
|  | const byte * | inString,
|  | size_t | length |
| ) |  |  | `[pure virtual, inherited]`

encrypt or decrypt an array of bytes of specified length

Note:
  either inString == outString, or they don't overlap

Implemented in Weak1::ARC4_Base, AuthenticatedSymmetricCipherBase, and PublicBlumBlumShub.

Referenced by AuthenticatedSymmetricCipherBase::ProcessData(), and StreamTransformation::ProcessLastBlock().

void StreamTransformation::ProcessLastBlock | ( | byte * | outString,
|  | const byte * | inString,
|  | size_t | length |
| ) |  |  | `[virtual, inherited]`

for ciphers where the last block of data is special, encrypt or decrypt the last block of data

For now the only use of this function is for CBC-CTS mode.

Definition at line 187 of file cryptlib.cpp.

References Algorithm::AlgorithmName(), StreamTransformation::MandatoryBlockSize(), StreamTransformation::MinLastBlockSize(), and StreamTransformation::ProcessData().

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

- cryptlib.h