Modern and easy-to-use crypto library Formula was removed
Last versions were
php71-libsodium@1.0 requires the following formulae to be installed:
autoconf 2.69 Automatic configure script builder
libsodium 1.0.16 NaCl networking and cryptography library

Recent formula history

Mike McQuaid Deprecate tap.
Jan Viljanen php7{01}-libsodium@1.0 1.0.7
Maarten de Boer Update (lib)sodium to 2.x for PHP 7.0 and 7.1 and rename to sodium

Formula code at GitHub