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