… or /dev/random in user space
The Entropy Source and DRNG Manager (ESDM) manages a set of deterministic random number generators (DRNG) and ensures their proper seeding and reseeding. To seed the DRNGs, a set of entropy sources are managed by the ESDM. The cryptographic strength of the entire ESDM is always 256 bits. All entropy processing is designed to maintain this strength.
Besides other services, it provides an API and ABI compliant drop-in
replacement for the Linux
/dev/urandom devices as well
getrandom system call. This means it not only supports common
users requesting random numbers, but also services using the IOCTLs
random(4) or using
poll(2) on the device files.
In addition to the Linux interface support, the ESDM provides a daemon managing
the entropy sources and DRNG instances that can be accessed with a wrapper
library. The ESDM requires only POSIX support along with
protobuf-c and thus
is intended to be executable on different operating systems.
It is extensible as follows:
Additional entropy sources can easily be added, existing entropy sources can be deselected during compile time or its entropy rate altered during startup time.
The cryptographic primitives can be altered by simply providing a new backend for hash algorithms or DRNG algorithms. See the
drng_chacha20configuration option replacing the SP800-90A DRBG with a ChaCha20-based DRNG, or the
hash_sha3_512configuration option replacing the SHA2-512 conditioning hash with SHA3-512.
Different DRNG Seeding strategies can be defined, by modifying one location in the code that governs the initial and reseeding operation of the DRNGs.
The (re)seeding operation of the DRNG implements design ideas of the following specifications:
SP800-90B: The entropy source of the Jitter RNG provides an SP800-90B compliant entropy source. In addition, the Intel RDSEED instruction is claimed to provide an SP800-90B entropy source. Also, when using the scheduler-based entropy source - which is only implemented for the Linux kernel using the code in
addon/linux_esdm_es, a separate SP800-90B entropy source is provided. In addition, when using the interrupt-based entropy source - which is only implemented for the Linux kernel using the code in
addon/linux_esdm_es, a separate SP800-90B entropy source is provided. If the kernel-based jitter entropy source shall be used, please compile your Linux kernel with CONFIG_CRYPTO_JITTERENTROPY.
SP800-90C: The specification provides guidelines how to combine a DRNG and entropy sources.
Use the Meson/Ninja build infrastructure with the following steps:
meson setup build
meson compile -C build
meson install -C build
The following dependencies are required:
- protobuf-c: When enabling any code beyond the ESDM library, the protobuf-c support is needed. Either the package of your favorite distribution must be installed or obtain the sources from the Protobuf-C Github website.
The following dependencies are required provided the respective functionality is enabled during compile time:
Jitter RNG: If the Jitter RNG entropy source is enabled as a compile time option, install the Jitter RNG library from your distribution or from the Jitter RNG homepage.
kcapi library: If the kernel-based jitter source is enabled as a compile time option, the kcapi library is required, either from your distribution or from the libkcapi website.
SELinux library: If your system uses SELinux and you compile the CUSE device file support (compile time option), the SELinux library is needed for proper device file labeling. In this case, use the package from your distribution.
FUSE 3 library: If the CUSE daemons shall be compiled and are enabled as a compile time option, the FUSE 3 library is required either from your distribution or from the libfuse Github website.
Botan >= 3.0: If the Botan backend for cryptographic operations shall be used and is enabled as a compile time option, or if the Botan ESDM seed source shall be compiled when the compile time option is enabled get Botan either from your distribution or from the botan Github website.
OpenSSL >= 3.0: If the OpenSSL backend for cryptographic operations shall be used and is enabled as a compile time option, or if the OpenSSL ESDM seed source shall be compiled when the compile time option is enabled, obtain OpenSSL either from your distribution or from the OpenSSL website.
leancrypto: If the leancrypto backend for cryptographic operations shall be enabled during compile time, obtain leancrypto from the leancrypto website.
Beyond those dependencies, only POSIX support is required.
A public git repository is provided with Github
The reference to the applicable documentation is given with the various releases.