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Introduction to Cryptography

Cryptography is the process of scrambling information so that it can only be read by those people who know how to unscramble the data.

For example, you can make a rule that you will shift all letters in the alphabet by three letters. So the letter “A” is represented by “D”, “B” is represented by “E”, and so on. So the sentence “Mike Clark is a great guy.” would be shown (or encrypted) as “Njlf Dmbsl jt b hsfbu hvz.”


You could also randomly assign letters to represent other letters. Then to figure out the original message (or decrypt) , instead of trying all 25 alphabetic shifts, you would need to have the original matchings. The major problem with this type of encryption is the English language has many sequences of letters that are more common than others. For example, “e” is the most common vowel, while “t” is the most common consonant. If an encrypted message has lots of “uif” sequences, that word may be “the.” This is how you can solve cryptograms in the newspaper. Look at how frequently letters appear, and then “guess” the most common letter is actually an “e.” If you have several three-letter words ending in “e,” maybe that word is actually “the.” Then fill in the “t” and “h” letters to see if any other words appear. It’s just like playing Wheel of Fortune.

Over time, mathematicians have come up with more difficult algorithms (or formulas) to hide the original message. An easy way to do this is to remove spaces between words. “NjlfD mbslj tbhsf buhvz.” is harder to figure out than “Njlf Dmbsl jt b hsfbu hvz.” You can also remove capitalization to make it harder to figure out. “njlfd mbslj tbhsf buhvz.” is even harder because you can’t assume there are two names at the begining of the phrase.

There are hundreds of different encryption algorithms.