[#RSA_padding_check_X931]
= RSA_padding_check_X931
:mrdocs:

Verify ANSI X9.31 padding and recover the message (deprecated).

== Synopsis

Declared in `<openssl/rsa.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
[[deprecated]]
int
RSA_padding_check_X931(
    unsigned char* to,
    int tlen,
    unsigned char const* f,
    int fl,
    int rsa_len);
----

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

Length of the recovered message, or a negative value on error.

== Parameters

[cols="1,4"]
|===
| Name| Description
| *to*
| Destination buffer for the recovered message.
| *tlen*
| Capacity of `to` in bytes.
| *f*
| Encoded block to check.
| *fl*
| Length of `f` in bytes.
| *rsa_len*
| Expected RSA modulus size in bytes.
|===


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