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Diffstat (limited to 'src/lib/libcrypto/man/ECDH_compute_key.3')
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| 1 | .\" $OpenBSD: ECDH_compute_key.3,v 1.1 2019/08/19 13:08:26 schwarze Exp $ | ||
| 2 | .\" Copyright (c) 2019 Ingo Schwarze <schwarze@openbsd.org> | ||
| 3 | .\" | ||
| 4 | .\" Permission to use, copy, modify, and distribute this software for any | ||
| 5 | .\" purpose with or without fee is hereby granted, provided that the above | ||
| 6 | .\" copyright notice and this permission notice appear in all copies. | ||
| 7 | .\" | ||
| 8 | .\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES | ||
| 9 | .\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF | ||
| 10 | .\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR | ||
| 11 | .\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES | ||
| 12 | .\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN | ||
| 13 | .\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF | ||
| 14 | .\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. | ||
| 15 | .\" | ||
| 16 | .Dd $Mdocdate: August 19 2019 $ | ||
| 17 | .Dt ECDH_COMPUTE_KEY 3 | ||
| 18 | .Os | ||
| 19 | .Sh NAME | ||
| 20 | .Nm ECDH_compute_key , | ||
| 21 | .Nm ECDH_size | ||
| 22 | .Nd Elliptic Curve Diffie-Hellman key exchange | ||
| 23 | .Sh SYNOPSIS | ||
| 24 | .In openssl/ecdh.h | ||
| 25 | .Ft int | ||
| 26 | .Fo ECDH_compute_key | ||
| 27 | .Fa "void *out" | ||
| 28 | .Fa "size_t outlen" | ||
| 29 | .Fa "const EC_POINT *public_key" | ||
| 30 | .Fa "EC_KEY *ecdh" | ||
| 31 | .Fa "void *(*KDF)(const void *in, size_t inlen, void *out, size_t *outlen)" | ||
| 32 | .Fc | ||
| 33 | .Ft int | ||
| 34 | .Fo ECDH_size | ||
| 35 | .Fa "const EC_KEY *ecdh" | ||
| 36 | .Fc | ||
| 37 | .Sh DESCRIPTION | ||
| 38 | .Fn ECDH_compute_key | ||
| 39 | performs Elliptic Curve Diffie-Hellman key agreement. | ||
| 40 | It combines the private key contained in | ||
| 41 | .Fa ecdh | ||
| 42 | with the other party's | ||
| 43 | .Fa public_key , | ||
| 44 | takes the | ||
| 45 | .Fa x | ||
| 46 | component of the affine coordinates, | ||
| 47 | and optionally applies the key derivation function | ||
| 48 | .Fa KDF . | ||
| 49 | It stores the resulting symmetric key in the buffer | ||
| 50 | .Fa out , | ||
| 51 | which is | ||
| 52 | .Fa outlen | ||
| 53 | bytes long. | ||
| 54 | If | ||
| 55 | .Fa KDF | ||
| 56 | is | ||
| 57 | .Dv NULL , | ||
| 58 | .Fa outlen | ||
| 59 | must be at least | ||
| 60 | .Fn ECDH_size ecdh . | ||
| 61 | .Pp | ||
| 62 | .Fn ECDH_size | ||
| 63 | returns the number of bytes needed to store an affine coordinate of a | ||
| 64 | point on the elliptic curve used by | ||
| 65 | .Fa ecdh , | ||
| 66 | which is one eigth of the degree of the finite field underlying | ||
| 67 | that elliptic curve, rounded up to the next integer number. | ||
| 68 | .Sh RETURN VALUES | ||
| 69 | .Fn ECDH_compute_key | ||
| 70 | returns the length of the computed key in bytes or -1 if an error occurs. | ||
| 71 | .Pp | ||
| 72 | .Fn ECDH_size | ||
| 73 | returns the number of bytes needed to store an affine coordinate. | ||
| 74 | .Sh SEE ALSO | ||
| 75 | .Xr DH_generate_key 3 , | ||
| 76 | .Xr DH_size 3 , | ||
| 77 | .Xr EC_GROUP_new 3 , | ||
| 78 | .Xr EC_KEY_new 3 , | ||
| 79 | .Xr EC_POINT_new 3 , | ||
| 80 | .Xr X25519 3 | ||
| 81 | .Sh HISTORY | ||
| 82 | .Fn ECDH_compute_key | ||
| 83 | first appeared in OpenSSL 0.9.8 and has been available since | ||
| 84 | .Ox 4.5 . | ||
| 85 | .Pp | ||
| 86 | .Fn ECDH_size | ||
| 87 | first appeared in | ||
| 88 | .Ox 6.1 . | ||