Add doxygen documentation to the new ECP interface
Document the functions in the Elliptic Curve Point module hardware
acceleration to guide silicon vendors when implementing the drivers.
diff --git a/include/mbedtls/ecp_internal.h b/include/mbedtls/ecp_internal.h
index a9f5bc5..ff7d1cb 100644
--- a/include/mbedtls/ecp_internal.h
+++ b/include/mbedtls/ecp_internal.h
@@ -21,61 +21,253 @@
*
* This file is part of mbed TLS (https://tls.mbed.org)
*/
+
+/*
+ * References:
+ *
+ * SEC1 http://www.secg.org/index.php?action=secg,docs_secg
+ * GECC = Guide to Elliptic Curve Cryptography - Hankerson, Menezes, Vanstone
+ * FIPS 186-3 http://csrc.nist.gov/publications/fips/fips186-3/fips_186-3.pdf
+ * RFC 4492 for the related TLS structures and constants
+ *
+ * [Curve25519] http://cr.yp.to/ecdh/curve25519-20060209.pdf
+ *
+ * [2] CORON, Jean-S'ebastien. Resistance against differential power analysis
+ * for elliptic curve cryptosystems. In : Cryptographic Hardware and
+ * Embedded Systems. Springer Berlin Heidelberg, 1999. p. 292-302.
+ * <http://link.springer.com/chapter/10.1007/3-540-48059-5_25>
+ *
+ * [3] HEDABOU, Mustapha, PINEL, Pierre, et B'EN'ETEAU, Lucien. A comb method to
+ * render ECC resistant against Side Channel Attacks. IACR Cryptology
+ * ePrint Archive, 2004, vol. 2004, p. 342.
+ * <http://eprint.iacr.org/2004/342.pdf>
+ */
+
#ifndef MBEDTLS_ECP_INTERNAL_H
#define MBEDTLS_ECP_INTERNAL_H
#if defined(MBEDTLS_ECP_INTERNAL_ALT)
+/**
+ * \brief Tell if the cryptographic hardware can handle the group.
+ *
+ * \param grp The pointer to the group.
+ *
+ * \return Non-zero if successful.
+ */
unsigned char mbedtls_internal_ecp_grp_capable( const mbedtls_ecp_group *grp );
+/**
+ * \brief Initialise the crypto hardware accelerator.
+ *
+ * If mbedtls_internal_ecp_grp_capable returns true for a
+ * group, this function has to be able to initialise the
+ * hardware for it.
+ *
+ * \param grp The pointer to the group the hardware needs to be
+ * initialised for.
+ *
+ * \return 0 if successful.
+ */
int mbedtls_internal_ecp_init( const mbedtls_ecp_group *grp );
+/**
+ * \brief Reset the crypto hardware accelerator to an uninitialised
+ * state.
+ *
+ * \param grp The pointer to the group the hardware was initialised for.
+ */
void mbedtls_internal_ecp_free( const mbedtls_ecp_group *grp );
+#if defined(ECP_SHORTWEIERSTRASS)
+
#if defined(MBEDTLS_ECP_RANDOMIZE_JAC_ALT)
+/**
+ * \brief Randomize jacobian coordinates:
+ * (X, Y, Z) -> (l^2 X, l^3 Y, l Z) for random l.
+ *
+ * This is sort of the reverse operation of
+ * ecp_normalize_jac().
+ *
+ * \param grp Pointer to the group representing the curve.
+ *
+ * \param pt The point on the curve to be randomised, given with Jacobian
+ * coordinates.
+ *
+ * \param f_rng A function pointer to the random number generator.
+ *
+ * \param p_rng A pointer to the random number generator state.
+ *
+ * \return 0 if successful.
+ */
int mbedtls_internal_ecp_randomize_jac( const mbedtls_ecp_group *grp,
mbedtls_ecp_point *pt, int (*f_rng)(void *, unsigned char *, size_t),
void *p_rng );
#endif
#if defined(MBEDTLS_ECP_ADD_MIXED_ALT)
+/**
+ * \brief Addition: R = P + Q, mixed affine-Jacobian coordinates.
+ *
+ * The coordinates of Q must be normalized (= affine),
+ * but those of P don't need to. R is not normalized.
+ *
+ * Special cases: (1) P or Q is zero, (2) R is zero,
+ * (3) P == Q.
+ * None of these cases can happen as intermediate step in
+ * ecp_mul_comb():
+ * - at each step, P, Q and R are multiples of the base
+ * point, the factor being less than its order, so none of
+ * them is zero;
+ * - Q is an odd multiple of the base point, P an even
+ * multiple, due to the choice of precomputed points in the
+ * modified comb method.
+ * So branches for these cases do not leak secret information.
+ *
+ * We accept Q->Z being unset (saving memory in tables) as
+ * meaning 1.
+ *
+ * Cost in field operations if done by GECC 3.22:
+ * 1A := 8M + 3S
+ *
+ * \param grp Pointer to the group representing the curve.
+ *
+ * \param R Pointer to a point structure to hold the result.
+ *
+ * \param P Pointer to the first summand, given with Jacobian
+ * coordinates
+ *
+ * \param Q Pointer to the second summand, given with affine
+ * coordinates.
+ *
+ * \return 0 if successful.
+ */
int mbedtls_internal_ecp_add_mixed( const mbedtls_ecp_group *grp,
mbedtls_ecp_point *R, const mbedtls_ecp_point *P,
const mbedtls_ecp_point *Q );
#endif
+/**
+ * \brief Point doubling R = 2 P, Jacobian coordinates.
+ *
+ * Cost: 1D := 3M + 4S (A == 0)
+ * 4M + 4S (A == -3)
+ * 3M + 6S + 1a otherwise
+ * when the implementation is based on
+ * http://www.hyperelliptic.org/EFD/g1p/
+ * auto-shortw-jacobian.html#doubling-dbl-1998-cmo-2
+ * and standard optimizations are applied when curve parameter
+ * A is one of { 0, -3 }.
+ *
+ * \param grp Pointer to the group representing the curve.
+ *
+ * \param R Pointer to a point structure to hold the result.
+ *
+ * \param P Pointer to the point that has to be doubled, given with
+ * Jacobian coordinates.
+ *
+ * \return 0 if successful.
+ */
#if defined(MBEDTLS_ECP_DOUBLE_JAC_ALT)
int mbedtls_internal_ecp_double_jac( const mbedtls_ecp_group *grp,
mbedtls_ecp_point *R, const mbedtls_ecp_point *P );
#endif
+/**
+ * \brief Normalize jacobian coordinates of an array of (pointers to)
+ * points.
+ *
+ * Using Montgomery's trick to perform only one inversion mod P
+ * the cost is:
+ * 1N(t) := 1I + (6t - 3)M + 1S
+ * (See for example Cohen's "A Course in Computational
+ * Algebraic Number Theory", Algorithm 10.3.4.)
+ *
+ * Warning: fails (returning an error) if one of the points is
+ * zero!
+ * This should never happen, see choice of w in ecp_mul_comb().
+ *
+ * \param grp Pointer to the group representing the curve.
+ *
+ * \param T Array of pointers to the points to normalise.
+ *
+ * \param t_len Number of elements in the array.
+ *
+ * \return 0 if successful,
+ * an error if one of the points is zero.
+ */
#if defined(MBEDTLS_ECP_NORMALIZE_JAC_MANY_ALT)
int mbedtls_internal_ecp_normalize_jac_many( const mbedtls_ecp_group *grp,
mbedtls_ecp_point *T[], size_t t_len );
#endif
+/**
+ * \brief Normalize jacobian coordinates so that Z == 0 || Z == 1.
+ *
+ * Cost in field operations if done by GECC 3.2.1:
+ * 1N := 1I + 3M + 1S
+ *
+ * \param grp Pointer to the group representing the curve.
+ *
+ * \param pt pointer to the point to be normalised. This is an
+ * input/output parameter.
+ *
+ * \return 0 if successful.
+ */
#if defined(MBEDTLS_ECP_NORMALIZE_JAC_ALT)
int mbedtls_internal_ecp_normalize_jac( const mbedtls_ecp_group *grp,
mbedtls_ecp_point *pt );
#endif
+#endif /* ECP_SHORTWEIERSTRASS */
+
+#if defined(ECP_MONTGOMERY)
+
#if defined(MBEDTLS_ECP_DOUBLE_ADD_MXZ_ALT)
int mbedtls_internal_ecp_double_add_mxz( const mbedtls_ecp_group *grp,
mbedtls_ecp_point *R, mbedtls_ecp_point *S, const mbedtls_ecp_point *P,
const mbedtls_ecp_point *Q, const mbedtls_mpi *d );
#endif
+/**
+ * \brief Randomize projective x/z coordinates:
+ * (X, Z) -> (l X, l Z) for random l
+ * This is sort of the reverse operation of ecp_normalize_mxz().
+ *
+ * \param grp pointer to the group representing the curve
+ *
+ * \param P the point on the curve to be randomised given with
+ * projective coordinates. This is an input/output parameter.
+ *
+ * \param f_rng a function pointer to the random number generator
+ *
+ * \param p_rng a pointer to the random number generator state
+ *
+ * \return 0 if successful
+ */
#if defined(MBEDTLS_ECP_RANDOMIZE_MXZ_ALT)
int mbedtls_internal_ecp_randomize_mxz( const mbedtls_ecp_group *grp,
mbedtls_ecp_point *P, int (*f_rng)(void *, unsigned char *, size_t),
void *p_rng );
#endif
+/**
+ * \brief Normalize Montgomery x/z coordinates: X = X/Z, Z = 1.
+ *
+ * \param grp pointer to the group representing the curve
+ *
+ * \param P pointer to the point to be normalised. This is an
+ * input/output parameter.
+ *
+ * \return 0 if successful
+ */
#if defined(MBEDTLS_ECP_NORMALIZE_MXZ_ALT)
int mbedtls_internal_ecp_normalize_mxz( const mbedtls_ecp_group *grp,
mbedtls_ecp_point *P );
#endif
+#endif /* ECP_MONTGOMERY */
+
#endif /* MBEDTLS_ECP_INTERNAL_ALT */
#endif /* ecp_internal.h */
