Hash Class Reference

Abstract base class for cryptographic hash algorithms. More...

#include <Hash.h>

Inheritance diagram for Hash:

Public Member Functions
	Hash ()
	Constructs a new hash object.
virtual	~Hash ()
	Destroys this hash object. More...
virtual size_t	hashSize () const =0
	Size of the hash result from finalize(). More...
virtual size_t	blockSize () const =0
	Size of the internal block used by the hash algorithm. More...
virtual void	reset ()=0
	Resets the hash ready for a new hashing process. More...
virtual void	update (const void *data, size_t len)=0
	Updates the hash with more data. More...
virtual void	finalize (void *hash, size_t len)=0
	Finalizes the hashing process and returns the hash. More...
virtual void	clear ()=0
	Clears the hash state, removing all sensitive data, and then resets the hash ready for a new hashing process. More...
virtual void	resetHMAC (const void *key, size_t keyLen)=0
	Resets the hash ready for a new HMAC hashing process. More...
virtual void	finalizeHMAC (const void *key, size_t keyLen, void *hash, size_t hashLen)=0
	Finalizes the HMAC hashing process and returns the hash. More...

Protected Member Functions
void	formatHMACKey (void *block, const void *key, size_t len, uint8_t pad)
	Formats a HMAC key into a block. More...

Detailed Description

Abstract base class for cryptographic hash algorithms.

See also

SHA224, SHA256, SHA384, SHA3_256, BLAKE2s

Definition at line 29 of file Hash.h.

Constructor & Destructor Documentation

~Hash()

Hash::~Hash ( )

virtual

Destroys this hash object.

Note

Subclasses are responsible for clearing any sensitive data that remains in the hash object when it is destroyed.

See also

clear()

Definition at line 48 of file Hash.cpp.

Member Function Documentation

blockSize()

size_t Hash::blockSize ( ) const

pure virtual

Size of the internal block used by the hash algorithm.

See also

update(), hashSize()

Implemented in SHA1, SHA512, SHA3_512, SHA3_256, SHA256, BLAKE2s, and BLAKE2b.

clear()

void Hash::clear ( )

pure virtual

Clears the hash state, removing all sensitive data, and then resets the hash ready for a new hashing process.

See also

reset()

Implemented in SHA1, SHA512, SHA3_512, SHA3_256, SHA256, BLAKE2s, and BLAKE2b.

finalize()

void Hash::finalize ( void *  hash, size_t  len  )

pure virtual

Finalizes the hashing process and returns the hash.

Parameters

hash	The buffer to return the hash value in.
len	The length of the hash buffer, normally hashSize().

If len is less than hashSize(), then the hash value will be truncated to the first len bytes. If len is greater than hashSize(), then the remaining bytes will left unchanged.

If finalize() is called again, then the returned hash value is undefined. Call reset() first to start a new hashing process.

See also

reset(), update(), finalizeHMAC()

Implemented in SHA1, SHA512, SHA3_512, SHA3_256, SHA256, BLAKE2s, and BLAKE2b.

finalizeHMAC()

void Hash::finalizeHMAC ( const void *  key, size_t  keyLen, void *  hash, size_t  hashLen  )

pure virtual

Finalizes the HMAC hashing process and returns the hash.

Parameters

key	Points to the HMAC key for the hashing process. The contents of this array must be identical to the value passed to resetHMAC().
keyLen	Size of the HMAC key in bytes.
hash	The buffer to return the hash value in.
hashLen	The length of the hash buffer, normally hashSize().

See also

resetHMAC(), finalize()

Implemented in SHA1, SHA512, SHA3_512, SHA3_256, SHA256, BLAKE2s, and BLAKE2b.

formatHMACKey()

void Hash::formatHMACKey ( void *  block, const void *  key, size_t  len, uint8_t  pad  )

protected

Formats a HMAC key into a block.

Parameters

block	The block to format the key into. Must be at least blockSize() bytes in length.
key	Points to the HMAC key for the hashing process.
len	Length of the HMAC key in bytes.
pad	Inner (0x36) or outer (0x5C) padding value to XOR with the formatted HMAC key.

This function is intended to help subclasses implement resetHMAC() and finalizeHMAC() by directly formatting the HMAC key into the subclass's internal block buffer and resetting the hash.

Definition at line 162 of file Hash.cpp.

hashSize()

size_t Hash::hashSize ( ) const

pure virtual

Size of the hash result from finalize().

See also

finalize(), blockSize()

Implemented in SHA1, SHA512, SHA384, SHA3_512, SHA3_256, SHA256, SHA224, BLAKE2s, and BLAKE2b.

reset()

void Hash::reset ( )

pure virtual

Resets the hash ready for a new hashing process.

See also

update(), finalize(), resetHMAC()

Implemented in SHA1, SHA512, SHA384, SHA3_512, SHA3_256, SHA256, SHA224, BLAKE2s, and BLAKE2b.

resetHMAC()

void Hash::resetHMAC ( const void *  key, size_t  keyLen  )

pure virtual

Resets the hash ready for a new HMAC hashing process.

Parameters

key	Points to the HMAC key for the hashing process.
keyLen	Size of the HMAC key in bytes.

The following example computes a HMAC over a series of data blocks with a specific key:

hash.resetHMAC(key, sizeof(key));
hash.update(data1, sizeof(data1));
hash.update(data2, sizeof(data2));
...
hash.update(dataN, sizeof(dataN));
hash.finalizeHMAC(key, sizeof(key), hmac, sizeof(hmac));

The same key must be passed to both resetHMAC() and finalizeHMAC().

See also

finalizeHMAC(), reset()

Implemented in SHA1, SHA512, SHA3_512, SHA3_256, SHA256, BLAKE2s, and BLAKE2b.

update()

void Hash::update ( const void *  data, size_t  len  )

pure virtual

Updates the hash with more data.

Parameters

data	Data to be hashed.
len	Number of bytes of data to be hashed.

If finalize() has already been called, then the behavior of update() will be undefined. Call reset() first to start a new hashing process.

See also

reset(), finalize()

Implemented in SHA1, SHA512, SHA3_512, SHA3_256, SHA256, BLAKE2s, and BLAKE2b.

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

• Hash.h
• Hash.cpp