File Information
Library: Foundation
Package: Crypt
Header: Poco/DigestEngine.h
Description
This class is an abstract base class for all classes implementing a message digest algorithm, like MD5Engine and SHA1Engine. Call update() repeatedly with data to compute the digest from. When done, call digest() to obtain the message digest.
Inheritance
Known Derived Classes: PBKDF2Engine, SHA2Engine, SHA1Engine, HMACEngine, Poco::Crypto::ECDSADigestEngine, Poco::Crypto::RSADigestEngine, Poco::Crypto::DigestEngine, MD4Engine, MD5Engine
Member Summary
Member Functions: constantTimeEquals, digest, digestFromHex, digestLength, digestToHex, reset, update, updateImpl
Types Aliases
Digest
using Digest = std::vector < unsigned char >;
Constructors
DigestEngine
DigestEngine();
Destructor
~DigestEngine 
virtual ~DigestEngine();
Member Functions
constantTimeEquals 
static bool constantTimeEquals(
const Digest & d1,
const Digest & d2
);
Compares two Digest values using a constant-time comparison algorithm. This can be used to prevent timing attacks (as discussed in <https://codahale.com/a-lesson-in-timing-attacks/>).
digest
virtual const Digest & digest() = 0;
Finishes the computation of the digest and returns the message digest. Resets the engine and can thus only be called once for every digest. The returned reference is valid until the next time digest() is called, or the engine object is destroyed.
digestFromHex
static Digest digestFromHex(
const std::string & digest
);
Converts a string created by digestToHex back to its Digest presentation
digestLength
virtual std::size_t digestLength() const = 0;
Returns the length of the digest in bytes.
digestToHex
static std::string digestToHex(
const Digest & bytes
);
Converts a message digest into a string of hexadecimal numbers.
reset
virtual void reset() = 0;
Resets the engine so that a new digest can be computed.
update 
void update(
const void * data,
std::size_t length
);
update
void update(
char data
);
update
void update(
const std::string & data
);
Updates the digest with the given data.
updateImpl 
virtual void updateImpl(
const void * data,
std::size_t length
) = 0;
Updates the digest with the given data. Must be implemented by subclasses.