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#ifndef _IPXE_X25519_H
#define _IPXE_X25519_H
/** @file
*
* X25519 key exchange
*
*/
FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
#include <stdint.h>
#include <ipxe/bigint.h>
/** X25519 unsigned big integer size
*
* X25519 uses the finite field of integers modulo the prime
* p=2^255-19. The canonical representations of integers in this
* field therefore require only 255 bits.
*
* For internal calculations we use big integers containing up to 267
* bits, since this ends up allowing us to avoid some unnecessary (and
* expensive) intermediate reductions modulo p.
*/
#define X25519_SIZE bigint_required_size ( ( 267 /* bits */ + 7 ) / 8 )
/** An X25519 unsigned big integer used in internal calculations */
typedef bigint_t ( X25519_SIZE ) x25519_t;
/** An X25519 unsigned 258-bit integer
*
* This is an unsigned integer N in the finite field of integers
* modulo the prime p=2^255-19.
*
* In this representation, N is encoded as any big integer that is in
* the same congruence class as N (i.e that has the same value as N
* modulo p) and that lies within the 258-bit range [0,8p-1].
*
* This type can be used as an input for multiplication (but not for
* addition or subtraction).
*
* Addition or subtraction will produce an output of this type.
*/
union x25519_oct258 {
/** Big integer value */
x25519_t value;
};
/** An X25519 unsigned 257-bit integer
*
* This is an unsigned integer N in the finite field of integers
* modulo the prime p=2^255-19.
*
* In this representation, N is encoded as any big integer that is in
* the same congruence class as N (i.e that has the same value as N
* modulo p) and that lies within the 257-bit range [0,4p-1].
*
* This type can be used as an input for addition, subtraction, or
* multiplication.
*
* Multiplication will produce an output of this type.
*/
union x25519_quad257 {
/** Big integer value */
x25519_t value;
/** X25519 unsigned 258-bit integer
*
* Any value in the range [0,4p-1] is automatically also
* within the range [0,8p-1] and so may be consumed as an
* unsigned 258-bit integer.
*/
const union x25519_oct258 oct258;
};
/** An X25519 32-byte value */
struct x25519_value {
/** Raw value */
uint8_t raw[32];
};
extern void x25519_multiply ( const union x25519_oct258 *multiplicand,
const union x25519_oct258 *multiplier,
union x25519_quad257 *result );
extern void x25519_invert ( const union x25519_oct258 *invertend,
union x25519_quad257 *result );
extern void x25519_reduce ( union x25519_quad257 *value );
extern int x25519_key ( const struct x25519_value *base,
const struct x25519_value *scalar,
struct x25519_value *result );
#endif /* _IPXE_X25519_H */
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