[#BN_generate_prime_ex]
= BN_generate_prime_ex
:mrdocs:

Generate a probable prime of the requested size and congruence constraints.

== Synopsis

Declared in `<openssl/bn.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
int
BN_generate_prime_ex(
    xref:BIGNUM.adoc[BIGNUM]* ret,
    int bits,
    int safe,
    xref:BIGNUM.adoc[BIGNUM] const* add,
    xref:BIGNUM.adoc[BIGNUM] const* rem,
    xref:BN_GENCB.adoc[BN_GENCB]* cb);
----

== Return Value

1 on success, or 0 on failure.

== Parameters

[cols="1,4"]
|===
| Name| Description
| *ret*
| Destination BIGNUM for the prime.
| *bits*
| Desired bit length.
| *safe*
| Non‐zero to require a safe prime ((p‐1)/2 also prime).
| *add*
| Optional modulus for the constraint ret ≡ rem (mod add), or NULL.
| *rem*
| Optional residue for that constraint, or NULL (defaults to 1).
| *cb*
| Optional generation callback, or NULL.
|===


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