--Originally published at Ce qui est chouette
The brief description provided by Coursera‘s Cyptography I course by the University of Stanford paints cryptography as a tool for protecting information in computer systems. What I’ll attempt to cover in this post is cryptography’s real-world application, why it is needed.
First let’s deal with some basic stuff regarding cryptography, starting with the classic Alice, Bob and that bastard Eve who’s always meddling, she’s more of a Lilith if you asked me. Let’s say Alice has the sudden urge to communicate some secret message to Bob, perhaps she’s going to confess her love, but Eve also likes Bob, and Alice knows this. She can’t met Bob in person, Eve would find out, she lives close by and would get in the way. THANK GOD for the cryptography course Bob and Alice took years ago, where they learned about symmetric and asymmetric cryptography . . .
Sidenote to Explain Asymmetric and Symmetric Cryptography
Based on this post on Synopsys. Encryption uses an algorithm and a key to turn plaintext, the message, into ciphertext, the encrypted message that you can then send. Symmetric Encryption uses the same key for both encryption and decryption of a message, its fast and can be used for large amounts of data, like encrypting a hard drive, the hard part is keeping that key secured. Asymmetric encryption keeps a pair of keys, a private one and a public one, that can be distributed anywhere to interact with your messages. Plaintext encrypted with a private key can only be decrypted by its corresponding public counterpart, and vice versa. A message can also be signed using your private key, so that others may decrypt the signature with your public key and verify it was sent by you. This type of encryption, though, is slow and can only be used to encrypt data smaller than the key.
Back to the gossip
Alice decided to use Bob‘s public key to encrypt her confession, Eve had a man-in-the-middle software running in Bob‘s network, and caught the message, she didn’t understood it, however, and decided to let it through, ignorant to the fact that she was about to lose Bob, her Bob, to Alice‘s encrypted message. Bob received the message and recognized the gibberish as an encrypted message, like the ones he had worked with. Bob got a hold of his private key and decrypted the message, the surprising confession got to him, and to Eve‘s dismay, reciprocated.
That’s not reality! Well, Alice is the everyday user, Bob is the destination of every operation Alice does online, and Eve is third-parties, like government agencies, interfering in these interactions. This everyday interaction is why encryption is important, to keep your privacy. These third-parties’ goal is to break these encryption algorithms, by cracking it themselves or demanding a backdoor from the developers, which was the case in the FBI-Apple encryption dispute or the whole Snowden situation, of which there’s a cool John Oliver video.
– XOXO, crypto guy