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Author	SHA1	Message	Date
brian m. carlson	768e30ea27	hash: implement and use a context cloning function For all of our SHA-1 implementations and most of our SHA-256 implementations, the hash context we use is a real struct. For these implementations, it's possible to copy a hash context by making a copy of the struct. However, for our libgcrypt implementation, our hash context is a pointer. Consequently, copying it does not lead to an independent hash context like we intended. Fortunately, however, libgcrypt provides us with a handy function to copy hash contexts. Let's add a cloning function to the hash algorithm API, and use it in the one place we need to make a hash context copy. With this change, our libgcrypt SHA-256 implementation is fully functional with all of our other hash implementations. Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>	5 years ago
brian m. carlson	27dc04c545	sha256: add an SHA-256 implementation using libgcrypt Generally, one gets better performance out of cryptographic routines written in assembly than C, and this is also true for SHA-256. In addition, most Linux distributions cannot distribute Git linked against OpenSSL for licensing reasons. Most systems with GnuPG will also have libgcrypt, since it is a dependency of GnuPG. libgcrypt is also faster than the SHA1DC implementation for messages of a few KiB and larger. For comparison, on a Core i7-6600U, this implementation processes 16 KiB chunks at 355 MiB/s while SHA1DC processes equivalent chunks at 337 MiB/s. In addition, libgcrypt is licensed under the LGPL 2.1, which is compatible with the GPL. Add an implementation of SHA-256 that uses libgcrypt. Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>	6 years ago
brian m. carlson	13eeedb5d1	Add a base implementation of SHA-256 support SHA-1 is weak and we need to transition to a new hash function. For some time, we have referred to this new function as NewHash. Recently, we decided to pick SHA-256 as NewHash. The reasons behind the choice of SHA-256 are outlined in the thread starting at [1] and in the commit history for the hash function transition document. Add a basic implementation of SHA-256 based off libtomcrypt, which is in the public domain. Optimize it and restructure it to meet our coding standards. Pull in the update and final functions from the SHA-1 block implementation, as we know these function correctly with all compilers. This implementation is slower than SHA-1, but more performant implementations will be introduced in future commits. Wire up SHA-256 in the list of hash algorithms, and add a test that the algorithm works correctly. Note that with this patch, it is still not possible to switch to using SHA-256 in Git. Additional patches are needed to prepare the code to handle a larger hash algorithm and further test fixes are needed. [1] https://public-inbox.org/git/20180609224913.GC38834@genre.crustytoothpaste.net/ Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>	6 years ago

Author

SHA1

Message

Date

brian m. carlson

768e30ea27

hash: implement and use a context cloning function

For all of our SHA-1 implementations and most of our SHA-256
implementations, the hash context we use is a real struct.  For these
implementations, it's possible to copy a hash context by making a copy
of the struct.

However, for our libgcrypt implementation, our hash context is a
pointer.  Consequently, copying it does not lead to an independent hash
context like we intended.

Fortunately, however, libgcrypt provides us with a handy function to
copy hash contexts.  Let's add a cloning function to the hash algorithm
API, and use it in the one place we need to make a hash context copy.
With this change, our libgcrypt SHA-256 implementation is fully
functional with all of our other hash implementations.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

5 years ago

brian m. carlson

27dc04c545

sha256: add an SHA-256 implementation using libgcrypt

Generally, one gets better performance out of cryptographic routines
written in assembly than C, and this is also true for SHA-256.  In
addition, most Linux distributions cannot distribute Git linked against
OpenSSL for licensing reasons.

Most systems with GnuPG will also have libgcrypt, since it is a
dependency of GnuPG.  libgcrypt is also faster than the SHA1DC
implementation for messages of a few KiB and larger.

For comparison, on a Core i7-6600U, this implementation processes 16 KiB
chunks at 355 MiB/s while SHA1DC processes equivalent chunks at 337
MiB/s.

In addition, libgcrypt is licensed under the LGPL 2.1, which is
compatible with the GPL.  Add an implementation of SHA-256 that uses
libgcrypt.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

6 years ago

brian m. carlson

13eeedb5d1

Add a base implementation of SHA-256 support

SHA-1 is weak and we need to transition to a new hash function.  For
some time, we have referred to this new function as NewHash.  Recently,
we decided to pick SHA-256 as NewHash.  The reasons behind the choice of
SHA-256 are outlined in the thread starting at [1] and in the commit
history for the hash function transition document.

Add a basic implementation of SHA-256 based off libtomcrypt, which is in
the public domain.  Optimize it and restructure it to meet our coding
standards.  Pull in the update and final functions from the SHA-1 block
implementation, as we know these function correctly with all compilers.
This implementation is slower than SHA-1, but more performant
implementations will be introduced in future commits.

Wire up SHA-256 in the list of hash algorithms, and add a test that the
algorithm works correctly.

Note that with this patch, it is still not possible to switch to using
SHA-256 in Git.  Additional patches are needed to prepare the code to
handle a larger hash algorithm and further test fixes are needed.

[1] https://public-inbox.org/git/20180609224913.GC38834@genre.crustytoothpaste.net/

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

6 years ago

3 Commits (645f63111b9fc456cc48da9b320b86800fe5477c)