Index: openssl/doc/crypto/EVP_PKEY_derive.pod |
=================================================================== |
--- openssl/doc/crypto/EVP_PKEY_derive.pod (revision 0) |
+++ openssl/doc/crypto/EVP_PKEY_derive.pod (revision 0) |
@@ -0,0 +1,93 @@ |
+=pod |
+ |
+=head1 NAME |
+ |
+EVP_PKEY_derive_init, EVP_PKEY_derive_set_peer, EVP_PKEY_derive - derive public key algorithm shared secret. |
+ |
+=head1 SYNOPSIS |
+ |
+ #include <openssl/evp.h> |
+ |
+ int EVP_PKEY_derive_init(EVP_PKEY_CTX *ctx); |
+ int EVP_PKEY_derive_set_peer(EVP_PKEY_CTX *ctx, EVP_PKEY *peer); |
+ int EVP_PKEY_derive(EVP_PKEY_CTX *ctx, unsigned char *key, size_t *keylen); |
+ |
+=head1 DESCRIPTION |
+ |
+The EVP_PKEY_derive_init() function initializes a public key algorithm |
+context using key B<pkey> for shared secret derivation. |
+ |
+The EVP_PKEY_derive_set_peer() function sets the peer key: this will normally |
+be a public key. |
+ |
+The EVP_PKEY_derive() derives a shared secret using B<ctx>. |
+If B<key> is B<NULL> then the maximum size of the output buffer is written to |
+the B<keylen> parameter. If B<key> is not B<NULL> then before the call the |
+B<keylen> parameter should contain the length of the B<key> buffer, if the call |
+is successful the shared secret is written to B<key> and the amount of data |
+written to B<keylen>. |
+ |
+=head1 NOTES |
+ |
+After the call to EVP_PKEY_derive_init() algorithm specific control |
+operations can be performed to set any appropriate parameters for the |
+operation. |
+ |
+The function EVP_PKEY_derive() can be called more than once on the same |
+context if several operations are performed using the same parameters. |
+ |
+=head1 RETURN VALUES |
+ |
+EVP_PKEY_derive_init() and EVP_PKEY_derive() return 1 for success and 0 |
+or a negative value for failure. In particular a return value of -2 |
+indicates the operation is not supported by the public key algorithm. |
+ |
+=head1 EXAMPLE |
+ |
+Derive shared secret (for example DH or EC keys): |
+ |
+ #include <openssl/evp.h> |
+ #include <openssl/rsa.h> |
+ |
+ EVP_PKEY_CTX *ctx; |
+ unsigned char *skey; |
+ size_t skeylen; |
+ EVP_PKEY *pkey, *peerkey; |
+ /* NB: assumes pkey, peerkey have been already set up */ |
+ |
+ ctx = EVP_PKEY_CTX_new(pkey); |
+ if (!ctx) |
+ /* Error occurred */ |
+ if (EVP_PKEY_derive_init(ctx) <= 0) |
+ /* Error */ |
+ if (EVP_PKEY_derive_set_peer(ctx, peerkey) <= 0) |
+ /* Error */ |
+ |
+ /* Determine buffer length */ |
+ if (EVP_PKEY_derive(ctx, NULL, &skeylen) <= 0) |
+ /* Error */ |
+ |
+ skey = OPENSSL_malloc(skeylen); |
+ |
+ if (!skey) |
+ /* malloc failure */ |
+ |
+ if (EVP_PKEY_derive(ctx, skey, &skeylen) <= 0) |
+ /* Error */ |
+ |
+ /* Shared secret is skey bytes written to buffer skey */ |
+ |
+=head1 SEE ALSO |
+ |
+L<EVP_PKEY_CTX_new(3)|EVP_PKEY_CTX_new(3)>, |
+L<EVP_PKEY_encrypt(3)|EVP_PKEY_encrypt(3)>, |
+L<EVP_PKEY_decrypt(3)|EVP_PKEY_decrypt(3)>, |
+L<EVP_PKEY_sign(3)|EVP_PKEY_sign(3)>, |
+L<EVP_PKEY_verify(3)|EVP_PKEY_verify(3)>, |
+L<EVP_PKEY_verifyrecover(3)|EVP_PKEY_verifyrecover(3)>, |
+ |
+=head1 HISTORY |
+ |
+These functions were first added to OpenSSL 1.0.0. |
+ |
+=cut |