An Introduction to Cryptography
The Fundamentals
Cryptography dates all the way back to the times of Julius Caesar. In its simplest terms, the science of cryptography is merely the scrambling and the descrambling of written messages between two individual parties.
These individual parties can also be referred to as the sender and the receiver. The former creates the text and scrambles it into an undecipherable state, and in turn, the latter receives the text and unscrambles it into a decipherable format.
A very simple example is “I LOVE YOU.” The sending party would scramble this message by rearranging the letters as “UYO I VEOL.” This message would then stay in this scrambled format while it is in transit, until it is received by the receiving party.
They would then descramble it, so it would read once again “I LOVE YOU.” If this message were to have been captured by a malicious third party, the content would be rendered useless and totally undecipherable. This is the essence of cryptography.
Specifically, it can be defined as:
“. . . creating written or generated codes that allow information to be kept secret. Cryptography converts data into a format that is unreadable for an unauthorized user, allowing it to be transmitted without unauthorized entities decoding it back into a readable format, thus compromising the data.”¹
Key Terminology
Scrambling and descrambling are also known as encryption and decryption, respectively.
- Plaintext (or Cleartext): The original, decrypted message in its understandable state (e.g., "I LOVE YOU").
- Ciphertext: The encrypted, garbled message that is meaningless to an unauthorized recipient (e.g., "UYO I VEOL").
The Digital Keys
How does this actually work? It happens through the use of a mechanism known as a key. This is very similar to a traditional physical key—you use it to lock your door when you leave and unlock it when you return. In the digital world, this is known as a Digital Key.
A digital key is based upon a mathematical value and is stored on the computers of both the sender and the receiver.
Symmetric Cryptography (Private Key)
In a symmetric system, both Party A and Party B use the exact same key to both scramble and descramble the message. While this provides security, it has an inherent flaw: if either party accidentally reveals the key to an outsider, the security of the entire system is eradicated.
Asymmetric Cryptography (Public & Private Keys)
To solve the "shared secret" problem, a newer system uses a pair of keys:
- Public Key: Used to scramble (encrypt) the message. As the name suggests, this key is not secret; anyone can have access to it.
- Private Key: Used to descramble (decrypt) the message. Only the recipient knows this key—not even the sender who used the public key has access to it.
This Public/Private Key combination offers a significantly higher layer of security and is the standard for modern digital communications.
[Image showing the difference between Symmetric (one key) and Asymmetric (two keys) encryption workflows]
Conclusions
This article has examined the fundamentals of cryptography. Of course, the field is much more complex, especially regarding the specific mathematical algorithms used for encryption and decryption. A future article will examine some of the more widely used algorithms in further detail.
