---
name: "kcapi_akcipher_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_akcipher_decrypt"
---

# kcapi\_akcipher\_decrypt(3)

decrypt data

## NAME

kcapi\_akcipher\_decrypt - decrypt data

## SYNOPSIS

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

## ARGUMENTS

*handle*

\[in\] cipher handle

*in*

\[in\] ciphertext data buffer

*inlen*

\[in\] length of in buffer

*out*

\[out\] plaintext data buffer

*outlen*

\[in\] length of out buffer

*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 decryption 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.

If the output size is insufficiently large, -EINVAL is returned. The output buffer must be at least as large as the modululs of the uses key.

*return* number of bytes returned by the decryption operation upon success; a negative errno-style error code if an error occurred

## AUTHOR

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

Author.

## COPYRIGHT