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for specialized Montgomery ladder implementations PR #6009 and #6070 replaced the default EC point multiplication path for prime and binary curves with a unified Montgomery ladder implementation with various timing attack defenses (for the common paths when a secret scalar is feed to the point multiplication). The newly introduced default implementation directly used EC_POINT_add/dbl in the main loop. The scaffolding introduced by this commit allows EC_METHODs to define a specialized `ladder_step` function to improve performances by taking advantage of efficient formulas for differential addition-and-doubling and different coordinate systems. - `ladder_pre` is executed before the main loop of the ladder: by default it copies the input point P into S, and doubles it into R. Specialized implementations could, e.g., use this hook to transition to different coordinate systems before copying and doubling; - `ladder_step` is the core of the Montgomery ladder loop: by default it computes `S := R+S; R := 2R;`, but specific implementations could, e.g., implement a more efficient formula for differential addition-and-doubling; - `ladder_post` is executed after the Montgomery ladder loop: by default it's a noop, but specialized implementations could, e.g., use this hook to transition back from the coordinate system used for optimizing the differential addition-and-doubling or recover the y coordinate of the result point. This commit also renames `ec_mul_consttime` to `ec_scalar_mul_ladder`, as it better corresponds to what this function does: nothing can be truly said about the constant-timeness of the overall execution of this function, given that the underlying operations are not necessarily constant-time themselves. What this implementation ensures is that the same fixed sequence of operations is executed for each scalar multiplication (for a given EC_GROUP), with no dependency on the value of the input scalar. Co-authored-by: Sohaib ul Hassan <soh.19.hassan@gmail.com> Co-authored-by: Billy Brumley <bbrumley@gmail.com> Reviewed-by: Andy Polyakov <appro@openssl.org> Reviewed-by: Matt Caswell <matt@openssl.org> (Merged from https://github.com/openssl/openssl/pull/6690) |
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| .. | ||
| build.info | ||
| err_all.c | ||
| err_prn.c | ||
| err.c | ||
| openssl.ec | ||
| openssl.txt | ||
| README | ||
Adding new libraries
--------------------
When adding a new sub-library to OpenSSL, assign it a library number
ERR_LIB_XXX, define a macro XXXerr() (both in err.h), add its
name to ERR_str_libraries[] (in crypto/err/err.c), and add
ERR_load_XXX_strings() to the ERR_load_crypto_strings() function
(in crypto/err/err_all.c). Finally, add an entry:
L XXX xxx.h xxx_err.c
to crypto/err/openssl.ec, and add xxx_err.c to the Makefile.
Running make errors will then generate a file xxx_err.c, and
add all error codes used in the library to xxx.h.
Additionally the library include file must have a certain form.
Typically it will initially look like this:
#ifndef HEADER_XXX_H
#define HEADER_XXX_H
#ifdef __cplusplus
extern "C" {
#endif
/* Include files */
#include <openssl/bio.h>
#include <openssl/x509.h>
/* Macros, structures and function prototypes */
/* BEGIN ERROR CODES */
The BEGIN ERROR CODES sequence is used by the error code
generation script as the point to place new error codes, any text
after this point will be overwritten when make errors is run.
The closing #endif etc will be automatically added by the script.
The generated C error code file xxx_err.c will load the header
files stdio.h, openssl/err.h and openssl/xxx.h so the
header file must load any additional header files containing any
definitions it uses.