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author | Dr. Stephen Henson <steve@openssl.org> | 2006-07-08 12:47:52 +0000 |
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committer | Dr. Stephen Henson <steve@openssl.org> | 2006-07-08 12:47:52 +0000 |
commit | ba702545fcab5e75181385c4415aa0d73a7022bb (patch) | |
tree | a7ca390e50dac5e78491ba9863f0a0dd457bba0f /doc/crypto | |
parent | 436369100d360d9119f2f77ed935d0c1f8f49d09 (diff) |
EVP_PKEY_derive() docs.
Diffstat (limited to 'doc/crypto')
-rw-r--r-- | doc/crypto/EVP_PKEY_derive.pod | 93 |
1 files changed, 93 insertions, 0 deletions
diff --git a/doc/crypto/EVP_PKEY_derive.pod b/doc/crypto/EVP_PKEY_derive.pod new file mode 100644 index 0000000000..99fa3090ee --- /dev/null +++ b/doc/crypto/EVP_PKEY_derive.pod @@ -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 0.9.9. + +=cut |