nettle-bugs September 2014

nettle-bugs@lists.lysator.liu.se

1 participants
6 discussions

ANNOUNCE: Nettle-3.0
by nisse＠lysator.liu.se 13 Apr '15

13 Apr '15

I'm happy to announce a new version of GNU Nettle, a low-level cryptographics library. The Nettle home page can be found at http://www.lysator.liu.se/~nisse/nettle/. This release is dual licensed as LGPLv3 or later, or GPLv2 or later. See the manual for details. NEWS for the Nettle 3.0 release This is a major release, including several interface changes, and new features, some of which are a bit experimental. Feedback is highly appreciated. It is *not* binary (ABI) compatible with earlier versions. It is mostly source-level (API) compatible, with a couple of incompatibilities noted below. The shared library names are libnettle.so.5.0 and libhogweed.so.3.0, with sonames libnettle.so.5 and libhogweed.so.3. There may be some problems in the new interfaces and new features which really need incompatible fixes. It is likely that there will be an update in the form of a 3.1 release in the not too distant future, with small but incompatible changes, and if that happens, bugfix-only releases 3.0.x are unlikely. Users and applications which desire better API and ABI stability are advised to stay with nettle-2.7.x (latest version is now 2.7.1) until the dust settles. Interface changes: * For the many _set_key functions, it is now consider the normal case to have a fixed key size, with no key_size arguments. _set_key functions with a length parameter are provided only for algorithms with a truly variable keysize, and where it makes sense for backwards compatibility. INCOMPATIBLE CHANGE: cast128_set_key no longer accepts a key size argument. The old function is available under a new name, cast5_set_key. INCOMPATIBLE CHANGE: The function typedef nettle_set_key_func no longer accepts a key size argument. In particular, this affects users of struct nettle_cipher. * The nettle_cipher abstraction (in nettle-meta.h) is restricted to block ciphers only. The encrypt and decrypt functions now take a const argument for the context. INCOMPATIBLE CHANGE: nettle_arcfour, i.e., the nettle_cipher abstraction for the arcfour stream cipher, is deleted. INCOMPATIBLE CHANGE: New type, nettle_cipher_func, for the encrypt and decrypt fields of struct nettle_cipher. * New DSA interface, with a separate struct dsa_param to represent the underlying group, and generalized dsa_sign and dsa_verify functions which don't care about the hash function used. Limited backwards compatibility provided in dsa-compat.h. INCOMPATIBLE CHANGE: Declarations of the old interface, e.g., struct dsa_public_key, dsa_sha1_sign, etc, is moved to dsa-compat.h. INCOMPATIBLE CHANGE: The various key conversion functions, e.g., dsa_keypair_to_sexp, all use the new DSA interface, with no backwards compatible functions. INCOMPATIBLE CHANGE: dsa_generate_keypair also uses the new interface. dsa-compat.h declares a function dsa_compat_generate_keypair, implementing the old interface, and #defines dsa_generate_keypair to refer to this backwards compatible function. * New AES and Camellia interfaces. There are now separate context structs for each key size, e.g., aes128_ctx and camellia256_ctx, and corresponding new functions. The old interface, with struct aes_ctx and struct camellia_ctx, is kept for backwards compatibility, but might be removed in later versions. * The type of most length arguments is changed from unsigned to size_t. The memxor functions have their pointer arguments changed from uint8_t * to void *, for consistency with related libc functions. * For hash functions, the constants *_DATA_SIZE have been renamed to *_BLOCK_SIZE. Old names kept for backwards compatibility. Removed features: * The nettle_next_prime function has been deleted. Applications should use GMP's mpz_nextprime instead. * Deleted the RSAREF compatibility, including the header file rsa-compat.h and everything declared therein. * Also under consideration for removal is des-compat.h and everything declared therein. This implements a subset of the old libdes/ssleay/openssl interface for DES and triple-DES, and it is poorly tested. If anyone uses this interface, please speak up! Otherwise, it will likely be removed in the next release. Bug fixes: * Building with ./configure --disable-static now works. * Use GMP's allocation functions for temporary storage related to bignums, to avoid potentially large stack allocations. * Fixes for shared libraries on M$ Windows. New features: * Support for Poly1305-AES MAC. * Support for the ChaCha stream cipher and EXPERIMENTAL support for the ChaCha-Poly1305 AEAD mode. Specifications are still in flux, and future releases may do incompatible changes to track standardization. Currently uses 256-bit key and 64-bit nonce. * Support for EAX mode. * Support for CCM mode. Contributed by Owen Kirby. * Additional variants of SHA512 with output size of 224 and 256 bits. Contributed by Joachim Strömbergson. * New interface, struct nettle_aead, for mechanisms providing authenticated encryption with associated data (AEAD). * DSA: Support a wider range for the size of q and a wider range for the digest size. Optimizations: * New x86_64 assembly for GCM and MD5. Modest speedups on the order of 10%-20%. Miscellaneous: * SHA3 is now documented as EXPERIMENTAL. Nettle currently implements SHA3 as specified at the time Keccak won the SHA3 competition. However, the final standard specified by NIST is likely to be incompatible, in which case future releases may do incompatible changes to track standardization. * The portability fix for the rotation macros, mentioned in NEWS for 2.7.1, actually didn't make it into that release. It is included now. * cast128_set_key rewritten for clarity, also eliminating a couple of compiler warnings. * New command line tool nettle-pbkdf2. Available at: https://ftp.gnu.org/gnu/nettle/nettle-3.0.tar.gz ftp://ftp.gnu.org/gnu/nettle/nettle-3.0.tar.gz http://www.lysator.liu.se/~nisse/archive/nettle-3.0.tar.gz ftp://ftp.lysator.liu.se/pub/security/lsh/nettle-3.0.tar.gz (soon) Happy hacking, /Niels Möller -- Niels Möller. PGP-encrypted email is preferred. Keyid C0B98E26. Internet email is subject to wholesale government surveillance.

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OCB mode
by Nikos Mavrogiannopoulos 28 Jan '15

28 Jan '15

Hello, What do you think of having OCB mode in nettle? I particularly like OCB due to it's simplicity and performance comparing to GCM/CCM, but was always patented. However in [0] there is license1 which states: "Under this license, you are authorized to make, use, and distribute open-source software implementations of OCB. This license terminates for you if you sue someone over their open-source software implementation of OCB claiming that you have a patent covering their implementation." What do you think? Should the FSF be consulted on that? regards, Nikos [0]. http://www.cs.ucdavis.edu/~rogaway/ocb/license.htm

4 8

curve25519 progress
by nisse＠lysator.liu.se 22 Oct '14

22 Oct '14

I've now pushed some crude code (on the curve25519 branch) which agrees with the test vectors in draft-josefsson-tls-curve25519-05. It uses the equivalent Edwards curve for the internal operations. For scalar multiplication of the fix generator, it uses Pippenger's algorithm and tables very similar to the other curves, just with different point operations and no special caes (since the Edwards operations are "complete"). At the end, the x-coordinate of the corresponding point on the Montgomery-form curve25519 is computed. For scalar multiplication of an arbitrary point (with only x coordinate provided), I first have to compute the y-coordinate using Shanks-Tonelli (this could be used to implement "point compression") also for other curves). Then transform to a point on the Edwards curve, using homogeneneous/projective coordinates. Then the actual scalar multiply is currently done with the binary algorithm; I have code for window-based scalar multiply, but it needs a bit more debugging. All this is very similar to the other corves, but without special cases. Regards, /Niels -- Niels Möller. PGP-encrypted email is preferred. Keyid C0B98E26. Internet email is subject to wholesale government surveillance.

4 18

ecc_curve and ecc_modulo
by nisse＠lysator.liu.se 24 Sep '14

24 Sep '14

I just pushed some reorganization of the ecc code. It introduces an internal struct ecc_modulo, which keeps the data and function pointers needed for modulo p (or modulo q) arithmetic. Immediate benefit was that a couple of wrapper functions could be deleted. E.g, ecc_generic_modp and ecc_generic_modq both called ecc_mod, but with different constants taken from different fields of struct ecc_curve). Now, one can instead call ecc_mod (&ecc->p, ...) and ecc_mod(&ecc->q, ...), respectively. I also added an invert function pointer, and wrote a specialized modp invert function for curve25519, which gives a nice little speedup. The code can be shared with sqrt, since the main part of the addition chain is the same for p-2 = 2^{255} - 21 (for invert) and (p-5)/8 = 2^{252} - 3 (for sqrt). Similar functions for the secp curves also make sense, at least for the mod p inversion; modq is less structured. The plan is to expand struct ecc_modulo with add, mul and sqr function pointers, to make it possible to have a different internal representation. In particular, using radix-51 for curve25519 modp arithmetic, on 64-bit machines. Regards, /Niels -- Niels Möller. PGP-encrypted email is preferred. Keyid C0B98E26. Internet email is subject to wholesale government surveillance.

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Hashing with EdDSA
by nisse＠lysator.liu.se 09 Sep '14

09 Sep '14

I'm looking into EdDSA. According to the paper, signing of a message M, using private key (a, k), corresponding to public key A, is essentially r = H(k | M), with k the second half of the private key R = rB, with B the specified generator of the curve, S = ((r + H(R | A | M) a) mod l, l is the curve order with some rules to encode R, A, S as strings. H is typically sha-512. If M is the original, arbitrarily long, message to be signed, this breaks the common structure that you can first compute a message digest, and then apply the secret key to produce a signature. But this doesn't work above, because the complete message has to be hashed twice, first with the secret prefix k, next with the prefix R | A, and any hashing without the private key available is useless. And even worse, one has to buffer the complete message because the prefix of the second hash depends on the output of the first hash. Or should M itself be a digest of the message to be signed? That will enable a more main-stream signature interface, where the inputs to the signature function are the private key and the short message digest. Regards, /Niels -- Niels Möller. PGP-encrypted email is preferred. Keyid C0B98E26. Internet email is subject to wholesale government surveillance.

2 4

Simplifying pic vs non-pic object files
by nisse＠lysator.liu.se 03 Sep '14

03 Sep '14

Currently, the nettle Makefile creates two object files for each source file, .o for inclusion in the static library, and .po ("pure object") for the shared library. By default, both are compiled as pic code, but --disable-pic drops the pic flags when compiling the .o files, to get non-pic code into the static library. I'm considering dropping this complication. Just build a single .o file, which is pic by default, and non-pic if --disable-pic is given. To build a non-pic static library, one would configure with "--disable-pic --disable-shared" (since just --disable-pic would produce a shared library with non-pic code, which is highly undesirable). And to produce a static non-pic library and a shared pic library, one would need to use separate build trees. Does that make sense? It would make things simpler, shorten build time, and eliminate the problem of naming two types of object files. One might also have --disable-pic imply --disable-shared (unless explicitly overridden by the user). Regards, /Niels -- Niels Möller. PGP-encrypted email is preferred. Keyid C0B98E26. Internet email is subject to wholesale government surveillance.

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nettle-bugs September 2014