A lightweight alternative to the official Travis Ruby CLI (only does environmental variable encryption)
travis-encrypt.sh is just a basic (hopefully portable) shell script. Simply download and run it, making sure you have a POSIX sh (bash, ksh, tcsh, zsh, etc.), openssl, curl, and sed.
Examples:
# Outputs encrypted result to stdout
./travis-encrypt.sh username/repo MYVAR=supersecret
# Outputs (via redirect) encrypted result to a file
./travis-encrypt.sh username/repo MYVAR=supersecret > encrypted_secure.txt