The Crypto method is a powerful tool which performs basic encryption and decryption which can be done so that each user will have a unique encrypted value, or a shared value. It uses OpenSSL to do all of its encryption, but more importantly its encrypted result is entirely URL friendly which enables you to use it as a UUID to be displayed in your URLs rather than obvious ID values.
Crypto::encrypt('testing'); // helper crypto_encrypt();
Crypto::decrypt('encrypted-text'); // helper crypto_decrypt();
Crypto::uuid(); // helper crypto_uuid();
The shareable as mentioned uses a common encryption key so that the encrypted values can be shared.