[#EVP_PBE_scrypt_ex]
= EVP_PBE_scrypt_ex
:mrdocs:

Derive a key from a password using scrypt with an explicit library context.

== Synopsis

Declared in `<openssl/evp.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
int
EVP_PBE_scrypt_ex(
    char const* pass,
    size_t passlen,
    unsigned char const* salt,
    size_t saltlen,
    uint64_t N,
    uint64_t r,
    uint64_t p,
    uint64_t maxmem,
    unsigned char* key,
    size_t keylen,
    xref:OSSL_LIB_CTX.adoc[OSSL_LIB_CTX]* ctx,
    char const* propq);
----

== Return Value

1 on success, or 0 on failure.

== Parameters

[cols="1,4"]
|===
| Name| Description
| *pass*
| Password bytes, or NULL.
| *passlen*
| Length of `pass` in bytes.
| *salt*
| Salt bytes, or NULL when `saltlen` is 0.
| *saltlen*
| Length of `salt` in bytes.
| *N*
| CPU/memory cost parameter (must be a power of two greater than 1).
| *r*
| Block size parameter.
| *p*
| Parallelization parameter.
| *maxmem*
| Maximum memory in bytes the derivation may use, or 0 for the default limit.
| *key*
| Buffer that receives the derived key.
| *keylen*
| Desired derived key length in bytes.
| *ctx*
| Library context for provider selection, or NULL for the default.
| *propq*
| Property query string, or NULL.
|===


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