[#EVP_PKEY_sign]
= EVP_PKEY_sign
:mrdocs:

Create a signature over data using an initialized signing context.

== Synopsis

Declared in `<openssl/evp.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
int
EVP_PKEY_sign(
    xref:EVP_PKEY_CTX.adoc[EVP_PKEY_CTX]* ctx,
    unsigned char* sig,
    size_t* siglen,
    unsigned char const* tbs,
    size_t tbslen);
----

== Return Value

1 on success, 0 or a negative value on failure.

== Parameters

[cols="1,4"]
|===
| Name| Description
| *ctx*
| Context previously prepared with EVP_PKEY_sign_init() (and optional controls).
| *sig*
| Output buffer for the signature, or NULL to only query the required length.
| *siglen*
| On entry, capacity of `sig` when non‐NULL; on return, signature length in bytes.
| *tbs*
| Message or digest bytes to sign.
| *tbslen*
| Length of `tbs` in bytes.
|===


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