Module org.eclipse.jgit

Package org.eclipse.jgit.util.sha1

Class SHA1

java.lang.Object

org.eclipse.jgit.util.sha1.SHA1

public class SHA1
extends Object

Pure Java implementation of SHA-1 from FIPS 180-1 / RFC 3174.

See RFC 3174.

Unlike MessageDigest, this implementation includes the algorithm used by sha1dc to detect cryptanalytic collision attacks against SHA-1, such as the one used by SHAttered. See sha1collisiondetection for more information.

When detectCollision is true (default), this implementation throws Sha1CollisionException from any digest method if a potential collision was detected.

Since:

4.7

Method Summary

Modifier and Type	Method	Description
byte[]	digest()	Finish the digest and return the resulting hash.
void	digest(MutableObjectId id)	Finish the digest and return the resulting hash.
boolean	hasCollision()	Check if a collision was detected.
static SHA1	newInstance()	Create a new context to compute a SHA-1 hash of data.
SHA1	reset()	Reset this instance to compute another hash.
SHA1	setDetectCollision(boolean detect)	Enable likely collision detection.
ObjectId	toObjectId()	Finish the digest and return the resulting hash.
void	update(byte b)	Update the digest computation by adding a byte.
void	update(byte[] in)	Update the digest computation by adding bytes to the message.
void	update(byte[] in, int p, int len)	Update the digest computation by adding bytes to the message.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

newInstance

public static SHA1 newInstance()

Create a new context to compute a SHA-1 hash of data.

Returns:

a new context to compute a SHA-1 hash of data.

setDetectCollision

public SHA1 setDetectCollision(boolean detect)

Enable likely collision detection.

Default is true.

May also be set by system property: -Dorg.eclipse.jgit.util.sha1.detectCollision=true.

Parameters:

detect - a boolean.

Returns:

this

update

public void update(byte b)

Update the digest computation by adding a byte.

Parameters:

b - a byte.

update

public void update(byte[] in)

Update the digest computation by adding bytes to the message.

Parameters:

in - input array of bytes.

update

public void update(byte[] in,
                   int p,
                   int len)

Update the digest computation by adding bytes to the message.

Parameters:

in - input array of bytes.

p - offset to start at from in.

len - number of bytes to hash.

digest

public byte[] digest()
              throws Sha1CollisionException

Finish the digest and return the resulting hash.

Once digest() is called, this instance should be discarded.

Returns:

the bytes for the resulting hash.

Throws:

Sha1CollisionException - if a collision was detected and safeHash is false.

toObjectId

public ObjectId toObjectId()
                    throws Sha1CollisionException

Finish the digest and return the resulting hash.

Once digest() is called, this instance should be discarded.

Returns:

the ObjectId for the resulting hash.

Throws:

Sha1CollisionException - if a collision was detected and safeHash is false.

digest

public void digest(MutableObjectId id)
            throws Sha1CollisionException

Finish the digest and return the resulting hash.

Once digest() is called, this instance should be discarded.

Parameters:

id - destination to copy the digest to.

Throws:

Sha1CollisionException - if a collision was detected and safeHash is false.

hasCollision

public boolean hasCollision()

Check if a collision was detected.

This method only returns an accurate result after the digest was obtained through digest(), digest(MutableObjectId) or toObjectId(), as the hashing function must finish processing to know the final state.

Returns:

true if a likely collision was detected.

reset

public SHA1 reset()

Reset this instance to compute another hash.

Returns:

this.