Initial Commit

openssl-1.0.2f/doc/crypto/EVP_PKEY_sign.pod

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+=pod
+
+=head1 NAME
+
+EVP_PKEY_sign_init, EVP_PKEY_sign - sign using a public key algorithm
+
+=head1 SYNOPSIS
+
+ #include <openssl/evp.h>
+
+ int EVP_PKEY_sign_init(EVP_PKEY_CTX *ctx);
+ int EVP_PKEY_sign(EVP_PKEY_CTX *ctx,
+			unsigned char *sig, size_t *siglen,
+			const unsigned char *tbs, size_t tbslen);
+
+=head1 DESCRIPTION
+
+The EVP_PKEY_sign_init() function initializes a public key algorithm
+context using key B<pkey> for a signing operation.
+
+The EVP_PKEY_sign() function performs a public key signing operation
+using B<ctx>. The data to be signed is specified using the B<tbs> and
+B<tbslen> parameters. If B<sig> is B<NULL> then the maximum size of the output
+buffer is written to the B<siglen> parameter. If B<sig> is not B<NULL> then
+before the call the B<siglen> parameter should contain the length of the
+B<sig> buffer, if the call is successful the signature is written to
+B<sig> and the amount of data written to B<siglen>.
+
+=head1 NOTES
+
+EVP_PKEY_sign() does not hash the data to be signed, and therefore is
+normally used to sign digests. For signing arbitrary messages, see the
+L<EVP_DigestSignInit(3)|EVP_DigestSignInit(3)> and
+L<EVP_SignInit(3)|EVP_SignInit(3)> signing interfaces instead.
+
+After the call to EVP_PKEY_sign_init() algorithm specific control
+operations can be performed to set any appropriate parameters for the
+operation (see L<EVP_PKEY_CTX_ctrl(3)|EVP_PKEY_CTX_ctrl(3)>).
+
+The function EVP_PKEY_sign() can be called more than once on the same
+context if several operations are performed using the same parameters.
+
+=head1 RETURN VALUES
+
+EVP_PKEY_sign_init() and EVP_PKEY_sign() 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
+
+Sign data using RSA with PKCS#1 padding and SHA256 digest:
+
+ #include <openssl/evp.h>
+ #include <openssl/rsa.h>
+
+ EVP_PKEY_CTX *ctx;
+ /* md is a SHA-256 digest in this example. */
+ unsigned char *md, *sig;
+ size_t mdlen = 32, siglen;
+ EVP_PKEY *signing_key;
+
+ /*
+  * NB: assumes signing_key and md are set up before the next
+  * step. signing_key must be an RSA private key and md must
+  * point to the SHA-256 digest to be signed.
+  */
+ ctx = EVP_PKEY_CTX_new(signing_key, NULL /* no engine */);
+ if (!ctx)
+	/* Error occurred */
+ if (EVP_PKEY_sign_init(ctx) <= 0)
+	/* Error */
+ if (EVP_PKEY_CTX_set_rsa_padding(ctx, RSA_PKCS1_PADDING) <= 0)
+	/* Error */
+ if (EVP_PKEY_CTX_set_signature_md(ctx, EVP_sha256()) <= 0)
+	/* Error */
+
+ /* Determine buffer length */
+ if (EVP_PKEY_sign(ctx, NULL, &siglen, md, mdlen) <= 0)
+	/* Error */
+
+ sig = OPENSSL_malloc(siglen);
+
+ if (!sig)
+	/* malloc failure */
+ 
+ if (EVP_PKEY_sign(ctx, sig, &siglen, md, mdlen) <= 0)
+	/* Error */
+
+ /* Signature is siglen bytes written to buffer sig */
+
+
+=head1 SEE ALSO
+
+L<EVP_PKEY_CTX_new(3)|EVP_PKEY_CTX_new(3)>,
+L<EVP_PKEY_CTX_ctrl(3)|EVP_PKEY_CTX_ctrl(3)>,
+L<EVP_PKEY_encrypt(3)|EVP_PKEY_encrypt(3)>,
+L<EVP_PKEY_decrypt(3)|EVP_PKEY_decrypt(3)>,
+L<EVP_PKEY_verify(3)|EVP_PKEY_verify(3)>,
+L<EVP_PKEY_verify_recover(3)|EVP_PKEY_verify_recover(3)>,
+L<EVP_PKEY_derive(3)|EVP_PKEY_derive(3)> 
+
+=head1 HISTORY
+
+These functions were first added to OpenSSL 1.0.0.
+
+=cut