---
name: "asn1_bit_der"
section: "3"
platform: "linux"
package: "libtasn1"
version: "4.21.0-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/asn1_bit_der"
---

# asn1\_bit\_der(3)

API function

## NAME

asn1\_bit\_der - API function

## SYNOPSIS

**#include \<libtasn1.h\>**

**void asn1\_bit\_der(const unsigned char \*** *str***, int** *bit\_len***, unsigned char \*** *der***, int \*** *der\_len***);**

## ARGUMENTS

- const unsigned char \* str

  BIT string.

- int bit\_len

  number of meaningful bits in STR.

- unsigned char \* der

  string returned.

- int \* der\_len

  number of meaningful bytes of DER (der\[0\]..der\[ans\_len-1\]).

## DESCRIPTION

Creates a length-value DER encoding for the input data as it would have been for a BIT STRING. The DER encoded data will be copied in  *der* .

Note that the BIT STRING tag is not included in the output.

This function does not return any value because it is expected that  *der\_len* will contain enough bytes to store the string plus the DER encoding. The DER encoding size can be obtained using **asn1\_length\_der()**.

## COPYRIGHT

Copyright © 2006-2025 Free Software Foundation, Inc..\
 Copying and distribution of this file, with or without modification, are permitted in any medium without royalty provided the copyright notice and this notice are preserved.

## SEE ALSO

The full documentation for **libtasn1** is maintained as a Texinfo manual.  If the **info** and **libtasn1** programs are properly installed at your site, the command

-

  **info libtasn1**

should give you access to the complete manual. As an alternative you may obtain the manual from:

-

  **https://www.gnu.org/software/libtasn1/manual/**