---
name: "kcapi_akcipher_sign"
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_sign"
---

# kcapi\_akcipher\_sign(3)

signature generation

## NAME

kcapi\_akcipher\_sign - signature generation

## SYNOPSIS

**ssize\_t kcapi\_akcipher\_sign(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*

\[in\] message data buffer

*inlen*

\[in\] length of in buffer

*out*

\[out\] signature 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 message and signature pointers. That would mean that after the signature generation operation, the message is overwritten with the signature.

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 signature gen operation upon success; a negative errno-style error code if an error occurred

## AUTHOR

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

Author.

## COPYRIGHT