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CSymmetricCipher Class Reference

class CSymmetricCipher : public CBase

Base Symmetric Cipher (abstract) class.

All cipher algorithms must be derived from this base class, which defines the IPSEC required API for cipher algorithms (used by ESP implementation).

Because IPSEC needs to run cipher for each packet independently, it is important that the implementation can reset the computation by InitL() without needing to do any additional allocations [which means that it being a leaving function is a bad sign!]

Inherits from

CSymmetricCipher
- CBase

Public Member Functions
	~CSymmetricCipher ()
void	Finish ( TDes8 &)
void	Init (const TDesC8 &, TAction )
TInt	Setkey (const TDesC8 &)
void	Update ( TDes8 &, const TDesC8 &)

Inherited Functions
	CBase::CBase()
	CBase::Delete(CBase *)
	CBase::Extension_(TUint,TAny &,TAny )
	CBase::operator new(TUint)
	CBase::operator new(TUint,TAny *)
	CBase::operator new(TUint,TLeave)
	CBase::operator new(TUint,TLeave,TUint)
	CBase::operator new(TUint,TUint)
	CBase::~CBase()

Public Member Enumerations
enum	TAction { EEncrypt , EDecrypt }

Constructor & Destructor Documentation

~CSymmetricCipher()

~CSymmetricCipher

(

)

[inline, virtual]

Member Functions Documentation

Finish(TDes8 &)

void

Finish

(

TDes8 &

aIV

)

[pure virtual]

Finish encryption or decryption.

Calling Finish is optional, it is needed if the total bytes is not multiple of the blocksize, or if one wants to get the final IV.

IPSEC does use the final IV.

Parameters

TDes8 & aIV

the place to return the final IV.

Init(const TDesC8 &, TAction)

void	Init	(	const TDesC8 &	aIV,
			TAction	aMode
		)	[pure virtual]

Reset the cipher engine to initial state.

As this method is called for each packet, it should not do any memory allocation or heavy computations.

Parameters

const TDesC8 & aIV	initial vector.
TAction aMode	tells whether initialize is for decrypt or encrypt.

Setkey(const TDesC8 &)

TInt

Setkey

(

const TDesC8 &

aKey

)

[pure virtual]

Define the cipher key.

Because setting the key can be time consuming, this is only called once after instantiation of the class. Then, each packet is started with a call to InitL.

Parameters

const TDesC8 & aKey

the cipher key. The length of the key is defined by the length of this descriptor, and is always multiple of 8 bits.

Update(TDes8 &, const TDesC8 &)

void	Update	(	TDes8 &	aOutbuf,
			const TDesC8 &	aInbuf
		)	[pure virtual]

Perform encryption or decryption.

Because algorithms are expected to work blocks, the caller will guarantee that ALL Outbuf's given to Update will exist up to Finish call (or at least as long as at least blocksize octets have been given to Update after it). The implementation of the algorithm can store pointer(s) to aOutbuf described memory area, and return data to such memory area on some later Update or Finish call.

The lengths of buffers are always equal, e.g. aInbuf.Length() octets will always fit into aOutbuf. This length can be anything from zero upwards. The cipher must work even if octets were fed to it one by one.

Parameters

TDes8 & aOutbuf	result of the decrypt/encrypt
const TDesC8 & aInbuf	input to decrypt/encrypt

Member Enumerations Documentation

Enum TAction

Enumerators

EEncrypt
EDecrypt