[#BN_mod_exp_mont]
= BN_mod_exp_mont
:mrdocs:

Compute modular exponentiation using Montgomery reduction: r = (a ˆ p) mod m.

== Synopsis

Declared in `<openssl/bn.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
int
BN_mod_exp_mont(
    xref:BIGNUM.adoc[BIGNUM]* r,
    xref:BIGNUM.adoc[BIGNUM] const* a,
    xref:BIGNUM.adoc[BIGNUM] const* p,
    xref:BIGNUM.adoc[BIGNUM] const* m,
    xref:BN_CTX.adoc[BN_CTX]* ctx,
    xref:BN_MONT_CTX.adoc[BN_MONT_CTX]* m_ctx);
----

== Return Value

1 on success, or 0 on error.

== Parameters

[cols="1,4"]
|===
| Name| Description
| *r*
| Destination for the result.
| *a*
| Base.
| *p*
| Exponent.
| *m*
| Modulus (must be odd).
| *ctx*
| BN_CTX scratch space.
| *m_ctx*
| Montgomery context for `m,` or NULL to build one temporarily.
|===


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