Psithyros

ψίθυρος ("psíthyros", Greek for "whisper") is an easy, minimal and user friendly graphical user interface wrapper around the open-source crypto library "pwcrypt", which is written entirely in C and Apache-2.0 licensed. The nerdy command line utility is free, the nice modern graphical user interface you pay for. Fair enough, right?

The concept is extremely simple: you enter a message into the input field, establish a password with your recipient (over a hopefully super secure channel) and encrypt the message symmetrically with that password. The output is just scrambled gibberish that only the most advanced alien civilizations can decipher (as of today). The recipient will then just copy & paste the encrypted ciphertext into the psíthyros input field, enter the correct password and hit decrypt. Boom! Cryptography made easy.

If you're a crypto nerd, here you go some additional details too:

Data is encrypted by deriving either an AES-256 (GCM) or ChaCha20-Poly1305 symmetric key using Argon2 with a random salt, then the input is compressed (unless the user disables compression), encrypted and Base64-encoded, ready to be sent to the recipient. Decryption occurs the same way (in reverse order). The time, memory and parallelism cost parameters for Argon2 are user-customizable inside the psíthyros settings menu, accessible via the round button at the top right corner.