[#ECDSA_do_sign_ex]
= ECDSA_do_sign_ex
:mrdocs:

Computes ECDSA signature of a given hash value using the supplied private key (note: sig must point to ECDSA_size(eckey) bytes of memory).

== Synopsis

Declared in `<openssl/ec.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
[[deprecated]]
xref:ECDSA_SIG.adoc[ECDSA_SIG]*
ECDSA_do_sign_ex(
    unsigned char const* dgst,
    int dgstlen,
    xref:BIGNUM.adoc[BIGNUM] const* kinv,
    xref:BIGNUM.adoc[BIGNUM] const* rp,
    xref:EC_KEY.adoc[EC_KEY]* eckey);
----

[WARNING]
====
https://en.cppreference.com/cpp/language/attributes/deprecated[Deprecated^]. Use of this entity is allowed but discouraged.
====
== Return Value

pointer to a ECDSA_SIG structure or NULL if an error occurred

== Parameters

[cols="1,4"]
|===
| Name| Description
| *dgst*
| pointer to the hash value to sign
| *dgstlen*
| length of the hash value
| *kinv*
| BIGNUM with a pre‐computed inverse k (optional)
| *rp*
| BIGNUM with a pre‐computed rp value (optional), see ECDSA_sign_setup
| *eckey*
| EC_KEY object containing a private EC key
|===


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