Article submission: End-to-end encryption and Captcha

[ahngo]

Hello, I'd like to submit two articles to be possibly added to your repository.

ELI5: End-to-end Encryption
https://medium.com/@cossacklabs/eli5-end-to-end-encryption-ae46821db74f

CAPTCHA: A brief history, its purpose and new versions
https://medium.com/@cyberalterego/everything-you-need-to-know-about-captcha-f77d65c56d2c