The tcb package contains core components of our tcb suite implementing the
alternative password shadowing scheme on Openwall GNU/*/Linux (Owl). It is
being made available separately from Owl primarily for use by other
distributions. For more information please refer to:

https://www.openwall.com/tcb/

To compile and use this you either need recent libxcrypt (which adopted the
password hashing API we had introduced in Owl) or our crypt_blowfish patched
into glibc (which is how we had introduced that API originally).

libxcrypt is available at:

https://github.com/besser82/libxcrypt

crypt_blowfish is available at:

https://www.openwall.com/crypt/