Take the example of stirring an egg. First, break the shell, pour the contents into a bowl and beat the contents vigorously until you get the necessary result, well, a scrambled egg. This action of mixing the egg molecules is encryption. Since the molecules are mixed, we say that the egg has reached a higher state of entropy (state of randomness). Returning the scrambled egg to its original shape (including decryption of the shell) is decrypted. Impossible?
However, if we replace the word “egg” and replace it with “number”, “molecules” with “digits”, it is POSSIBLE. This, my friend, is the exciting world of crypto (crypto for short). It is a new field dominated by talented mathematicians using vocabulary such as “nonlinear polynomial relations”, “overdefined systems of multivariate polynomial equations”, “Galois fields”, etc. These cryptographers use language that mere mortals like us cannot pretend to understand.
In the computer, everything stored is numbers. Your MP3 file is a number. Your text message is a number. Your address book is a longer number. The number 65 represents the character “A”, 97 for the small “a”, and so on.
For humans, we recognize numbers with the digits 0-9, where the computer can only recognize 0 or 1 otherwise. This is the binary system that uses bits instead of digits. To convert bits to digits, simply multiply the number of bits by 0.3 to get a good estimate. For example, if you have 256 bits of Indonesian rupiah (one of the lowest currency denominations in the world), the wealth of Bill Gates in comparison would be microscopic.
The hexadecimal system (base 16) uses the ten digits 0 through 9, plus the six additional symbols from A to F. This set has sixteen different “digits”, hence the hexadecimal name. This notation is useful for computer workers to take a look at the “real content” stored by the computer. Alternatively, treat these different number systems as currencies, be it Euro, Swiss Franc, Pound Sterling, and the like. Just as an object can be priced with different values using these currencies, a number can also have a “price” in these different number systems.
To deviate a little, have you ever wondered why you had to study prime numbers at school? I’m sure most of the math teachers don’t know this answer. Answer: A sub-branching called public key cryptography that uses prime numbers especially to encrypt emails. There, they are talking about even bigger numbers, like 2048, 4096, 8192 bits).
When we want to encrypt something, we need to use encryption. An encryption is just an algorithm similar to a recipe for baking a cake. It has precise and unequivocal steps. To carry out the encryption process, you need a key (some called it a passphrase). A good practice in quantstamp review requires that the key used by an encryption be of high entropy for it to be effective.
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