Signing and encrypting data with tools built-in to Rails

I have released that many people working with Ruby on Rails are not aware that it provides classes for signing and verifying messages and encrypting and decrypting them. ActiveSupport::MessageVerifier and ActiveSupport::MessageEncryptor are used by Rails to implement encrypted session stored in a browser cookie, but you can use them yourself to encrypt data.

Using both classes is simple. Here is an example of using MessageVerifier:

verifier ='your-secret')
message = "String that is prevented from tampering."
# Sign the message...
signed_message = verifier.generate(message)
# and verify it.
verified = verifier.verify(signed_message)

# Verified message equals the original message
verified == message #=> true

If the string is tampered #verify will raise ActiveSupport::MessageVerifier::InvalidSignature exception.

MessageEncryptor works in similar way:

salt  = SecureRandom.random_bytes(64)
key   ='password').

message = "Encrypted string."
encryptor =
# Encrypt the message...
encrypted_message = encryptor.encrypt_and_sign(message)
# and decrypt it.
decrypted = encryptor.decrypt_and_verify(encrypted_message)

# Decrypted message equals the original message
decrypted == message #=> true

If the string is tampered #decrypt_and_verify will raise ActiveSupport::MessageEncryptor::InvalidMessage exception.

Documentation is available for both MessageVerifier and MessageEncryptor. For real world example of using these facilities you can view how Rails uses them to implement encrypted cookies.

So the next time you need to encrypt data, you don’t have to implement your own (probably insecure) solution but you can reach for ActiveSupport.