---
name: "kcapi_cipher_decrypt"
section: "3"
platform: "linux"
package: "libkcapi-dev"
version: "1.4.0-1+b2"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/kcapi_cipher_decrypt"
---

# kcapi\_cipher\_decrypt(3)

decrypt data (synchronous one shot)

## NAME

kcapi\_cipher\_decrypt - decrypt data (synchronous one shot)

## SYNOPSIS

**ssize\_t kcapi\_cipher\_decrypt(struct kcapi\_handle \*** *handle***, const uint8\_t \*** *in***, size\_t** *inlen***, const uint8\_t \*** *iv***, uint8\_t \*** *out***, size\_t** *outlen***, int** *access***);**

## ARGUMENTS

*handle*

\[in\] cipher handle

*in*

\[in\] ciphertext data buffer

*inlen*

\[in\] length of in buffer

*iv*

\[in\] IV to be used for cipher operation

*out*

\[out\] plaintext data buffer

*outlen*

\[in\] length of out bufferS

*access*

\[in\] kernel access type (KCAPI\_ACCESS\_HEURISTIC - use internal heuristic for fastest kernel access; KCAPI\_ACCESS\_VMSPLICE - use vmsplice access; KCAPI\_ACCESS\_SENDMSG - sendmsg access)

## DESCRIPTION

It is perfectly legal to use the same buffer as the plaintext and ciphertext pointers. That would mean that after the encryption operation, the ciphertext is overwritten with the plaintext.

The memory should be aligned at the page boundary using posix\_memalign(sysconf(\_SC\_PAGESIZE)), If it is not aligned at the page boundary, the vmsplice call may not send all data to the kernel.

The IV buffer must be exactly **kcapi\_cipher\_ivsize** bytes in size.

*return* number of bytes decrypted upon success; a negative errno-style error code if an error occurred

## AUTHOR

**Stephan Mueller** \<smueller@chronox.de\>

Author.

## COPYRIGHT