[#BN_are_coprime]
= BN_are_coprime
:mrdocs:

Test whether `a` and `b` are coprime (gcd == 1), possibly mutating `a.`

== Synopsis

Declared in `<openssl/bn.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
int
BN_are_coprime(
    xref:BIGNUM.adoc[BIGNUM]* a,
    xref:BIGNUM.adoc[BIGNUM] const* b,
    xref:BN_CTX.adoc[BN_CTX]* ctx);
----

== Return Value

1 if gcd(|`a|,|b|)` == 1, 0 if not coprime, or a negative value on error.

== Parameters

[cols="1,4"]
|===
| Name| Description
| *a*
| First value; may be overwritten as a scratch during the gcd.
| *b*
| Second value (not modified).
| *ctx*
| BN_CTX scratch space.
|===


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