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

# kcapi-rng(1)

Kernel Crypto API Random Number Gatherer

## NAME

kcapi-rng - Kernel Crypto API Random Number Gatherer

## SYNOPSIS

**kcapi-rng** \[*OPTION*\]

## DESCRIPTION

The *kcapi-rng* application provides tool to obtain random numbers from the Linux kernel crypto API via the command line. The tool is similar to reading */dev/hwrand* with the difference that the used random number generators are fully deterministic - i.e. they are DRNGs.

Any potential seed data can be provided via STDIN. Some of the DRNGs require seeding as they do not seed themselves. The *kcapi-rng* tool ensures that the DRNGs are seeded by pulling the seed data from the *getrandom* system call (or */dev/urandom* if *getrandom* is not available). The amount of seed data is defined by the DRNG itself and can be reviewed by assessing */proc/crypto*. The seed provided via STDIN will be added to the internally-generated seed. The generated random numbers are written to STDOUT.

The following options are supported when invoking *kcapi-rng*:

- **-b**, **--bytes** *BYTES*

  Generate *BYTES* number of random bytes.

- **-n**, **--name** *NAME*

  The *NAME* argument specifies the random number generator implementation to be used. The allowed random number generators are defined by the Linux kernel. Currently registered ciphers can be reviewed at */proc/crypto*. The content of this file, however, can change when new ciphers are registered. The *NAME* argument is given directly to the Linux kernel crypto API. The chosen cipher must be of type *rng* as marked in */proc/crypto*. If this option is not used, the cipher *stdrng* is used as default.

- **--hex**

  The generated random numbers are print out in hexadecimal notation instead of as binary string.

- **-v**, **--verbose**

  Enable a verbose operation of *kcapi-rng*. Using this option multiple times increases the verbosity.

- **-q**, **--quiet**

  Prevent the generation of any log output.

- **-h**, **--help**

  Display the help text.

- **--version**

  Display the version number of the *kcapi-rng* application.

## SEE ALSO

[**kcapi-enc**(1)](/kcapi-enc/1.md) [**kcapi-dgst**(1)](/kcapi-dgst/1.md)