https://www.yahoo.com/tech/faq-how-encryption-works-and-why-people-are-so-18... Encryption has been all over the headlines after recent terrorist attacks, and the discussion can quickly get cryptic. Is “crypto” a fatal weakness of the Internet? An endangered species that must be saved? You can hear heartfelt testimony for either view from both Democratic and Republican politicians. But ultimately, encryption is just math that, like any other tool, can be used for good or ill. Let’s start with some basics about it that often get neglected in all the commentary. Q. It was my understanding there would be no math in this story…? A. Sorry, it’s unavoidable: Encryption works by encoding information in such a way that its recipient can decode it (without further help from its sender), but no one else can. To do that scrambling, you need to run the original data through one equation or another. For example, to encrypt something against the prying eyes of somebody who’s really, really drunk, you could just replace each letter with one 13 places forward (so “A” becomes “N” and so on). If your eavesdropper is more capable, you’ll need something more complicated — but it’s still all equations. Q. Okay. What makes for strong cryptography? A. Using more complex math in an encryption algorithm only goes so far if the sender and recipient use the same key — that is, if they both plug the same secret set of digits into the encryption formula — to encrypt and decrypt. In that case, if either party loses the key, game over.