Building

Sanctum builds out of the box on several different operating systems.

• MacOS 13 or higher
• Linux 5.x or higher
• OpenBSD 6.8 or higher

A default build requires at least pkg-config and libsodium. Note that on OpenBSD you will need to have gmake installed.

Caveat: libsodium on aarch64 platforms for most distros it not built correctly and aes-gcm support in libsodium is disabled due to this. See the encryption section for other options and how to enable them.

Building instructions:

$ git clone https://github.com/jorisvink/sanctum
$ cd sanctum
$ make
# make install

Customizing the build

Sanctum can be built with different cryptographic libraries, allowing you to build your own backend for each individual component.

Components can be mixed so that you for example build with one component for encryption but another one for x25519.

Even the KDF labels can be customized.

If you want to introduce your own backends please take a look at the mk/<component> paths and how the existing backends their .mk files are constructed.

KDF labels

All of the labels for the KDF that Sanctum uses (KMAC256) are prefixed with "SANCTUM.". This can be overriden to provide domain separation between applications or tunnels at compile time by specifying SANCTUM_KDF_PREFIX as a define under CFLAGS.

You may also choose to override the KDF labels specific to cathedral communication if you wish by setting SANCTUM_CATHEDRAL_KDF_PREFIX in the same manner.

$ CFLAGS=-DSANCTUM_KDF_PREFIX='\"MY_PREFIX.\"' make

$ CFLAGS=-DSANCTUM_KDF_PREFIX='\"MY_PREFIX.\"' \ -DSANCTUM_CATHEDRAL_KDF_PREFIX='\"CUSTOM_CATHEDRAL.\"' make

Encryption

For the encryption Sanctum comes with backends for the following libraries:

• nyfe-agelas
• libsodium-aegis
• libsodium-aes-gcm (default)
• mbedtls-aes-gcm (required mbedtls 3.x)

These can be selected by setting the CIPHER environment variable at compile time.

$ CIPHER=mbedtls-aes-gcm make

Classical ECDH

For the classical key exchange part of the hybrid key negotiation Sanctum comes with backends for the following libraries:

• libsodium-x25519 (default)
• mbedtls-x25519 (requires mbedtls 3.x)

These can be selected by setting the ASYMMETRY environment variable at compile time.

$ ASYMMETRY=mbedtls-x25519 make

PQ-secure KEM

For the PQ-secure key exchange part of the hybrid key negotiation Sanctum comes with backends for the following libraries:

• mlkem1024-ref (pqcrystals its reference implementation)

These can be selected by setting the KEM environment variable at compile time.

$ KEM=custom-kem-backend make

Random

For providing cryptographically strong random numbers Sanctum comes with backends for the following:

• nyfe-random

These can be selected by setting the PRNG environment variable at compile time.

$ PRNG=custom-random-backend make

Signature

For signing and signature verification Sanctum comes with backends for the following libraries:

• libsodium-ed25519

These can be selected by setting the SIGNATURE environment variable at compile time.

$ SIGNATURE=custom-signature-backend make