---
name: "shishi_decrypt_iv"
section: "3"
platform: "linux"
package: "shishi-doc"
version: "1.0.3-5"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/shishi_decrypt_iv"
---

# shishi\_decrypt\_iv(3)

API function

## NAME

shishi\_decrypt\_iv - API function

## SYNOPSIS

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

**int shishi\_decrypt\_iv(Shishi \*** *handle***, Shishi\_key \*** *key***, int** *keyusage***, const char \*** *iv***, size\_t** *ivlen***, const char \*** *in***, size\_t** *inlen***, char \*\*** *out***, size\_t \*** *outlen***);**

## ARGUMENTS

- Shishi \* handle

  shishi handle as allocated by **shishi\_init()**.

- Shishi\_key \* key

  key to decrypt with.

- int keyusage

  integer specifying what this key is decrypting.

- const char \* iv

  input array with initialization vector

- size\_t ivlen

  size of input array with initialization vector.

- const char \* in

  input array with data to decrypt.

- size\_t inlen

  size of input array with data to decrypt.

- char \*\* out

  output array with newly allocated decrypted data.

- size\_t \* outlen

  output variable with size of newly allocated output array.

## DESCRIPTION

Decrypts data using specified initialization vector and key.  The key actually used is derived using the key usage.  If key usage is 0, no key derivation is used.  The OUT buffer must be deallocated by the caller.  The next IV is lost, see shishi\_decrypt\_ivupdate\_etype if you need it.

Note that DECRYPT(ENCRYPT(data)) does not necessarily yield data exactly.  Some encryption types add pad to make the data fit into the block size of the encryption algorithm.  Furthermore, the pad is not guaranteed to look in any special way, although existing implementations often pad with the zero byte.  This means that you may have to "frame" data, so it is possible to infer the original length after decryption.  Compare ASN.1 DER which contains such information.

## RETURN VALUE

Returns **SHISHI\_OK** iff successful.

## REPORTING BUGS

Report bugs to \<bug-shishi@gnu.org\>. GNU Shishi home page: http://www.gnu.org/software/shishi/ General help using GNU software: http://www.gnu.org/gethelp/

## COPYRIGHT

Copyright © 2002-2022 Simon Josefsson.\
 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 **shishi** is maintained as a Texinfo manual.  If the **info** and **shishi** programs are properly installed at your site, the command

-

  **info shishi**

should give you access to the complete manual.