com.jcraft.jsch

Interface MAC

public interface MAC

Usually not to be used by applications. A Message Authentication Code algorithm which will be used by the library to make sure the messages are not tampered with.

This interface is a slimmed-down version of Mac.

The library gets the implementation class from a configuration option (with the name of the algorithm as key) and then instantiates an object using the no-argument constructor. The algorithms to be used are negotiated during key exchange.

The library includes two implementations for each of the algorithms hmac-sha1, hmac-sha1-96, hmac-md5, hmac-md5-96, one based on JCE's Mac class (available in Java SE from 1.4 on) and another one done manually (using MessageDigest). The latter ones are by default used on Mac OS X, the former ones on other systems.

See Also:

RFC 4253, Section 6.4, Data Integrity, RFC 2104, HMAC: Keyed-Hashing for Message Authentication, Mac

Method Summary

Modifier and Type	Method and Description
void	doFinal(byte[] buf, int offset) Finalizes the production of the digest, producing the digest value.
int	getBlockSize() The size of the produced MAC, i.e. the digest length, in bytes.
String	getName() The name of the algorithm, as defined in RFC 4253.
void	init(byte[] key) Initializes the MAC, providing the key.
void	update(byte[] foo, int start, int len) Updates the MAC with some data.
void	update(int foo) Updates the MAC with 4 bytes of data.

Method Detail

getName

String getName()

The name of the algorithm, as defined in RFC 4253.

Returns:

for the build-in algorithms, one of hmac-sha1, hmac-sha1-96, hmac-md5 and hmac-md5-96.

getBlockSize

int getBlockSize()

The size of the produced MAC, i.e. the digest length, in bytes.

init

void init(byte[] key)
   throws Exception

Initializes the MAC, providing the key.

Throws:

Exception

update

void update(byte[] foo,
            int start,
            int len)

Updates the MAC with some data.

Parameters:

foo - an array containing the data to authenticate.

start - the position in foo where the data starts.

len - the length of the data.

update

void update(int foo)

Updates the MAC with 4 bytes of data.

Parameters:

foo - a 32 bit value, which will be interpreted as 4 bytes in big-endian order.

doFinal

void doFinal(byte[] buf,
             int offset)

Finalizes the production of the digest, producing the digest value.

Parameters:

buf - an array to put the authentication code into.

offset - the position in buf where the output should begin.