Simplified definition: The practice of modifying data using mathematical algorithms so that only those it is intended for can read it.
The meaning of “cryptography” comes from the Greek, “kryptós” which means hidden, and “graphein” which means to write.
The original definition is simply more complicated, but will be explained like:
“Cryptography is the science of using mathematics to encrypt and decrypt data. Cryptography enables you to store sensitive information or transmit it across insecure networks (like the Internet) so that it cannot be read by anyone except the intended recipient.”
PGP Corporation, 2002
Core Principles of Modern Cryptography
Modern cryptography focuses on four major security goals:
- Secrecy
- Authenticity
- Integrity
- Non-repudiation
Together, these features of modern cryptography enable communications systems (e.g., HTTPS — the protocol your browser is currently using to securely communicate with Coinweb’s servers) to securely transfer billions of messages daily while effectively and efficiently hiding them from prying eyes.
1. Secrecy
The foremost purpose is to keep information secret from those it is not intended for.
This is achieved through encryption using algorithms, each with its own set of advantages and disadvantages (e.g., quantum resistance vs computational load). Here are a few popular encryption algorithms used today:
- Triple DES
- AES
- Blowfish
- Twofish
- RSA
2. Authenticity
A message receiver needs to be certain that incoming messages are coming from the expected sender, not a third party.
Authenticity is often verified with digital signatures — hashes of the original message made with the sender’s private key. The receiver then replicates and compares the hashes with the original. A mismatch of these hashes indicates the message is not authentic.
3. Integrity
Integrity is another essential element of the cryptographic puzzle.
When communicating, the sender and receiver need to know that what was sent is exactly what was received. Malicious actors may intercept messages and change them or substitute alternative ones.
4. Non-repudiation
In simple terms, repudiation means the refusal to accept something as true. Non-repudiation, in that case, would mean the inability to refuse the validity of something. In the case of cryptography, that’s the inability to refute a claim that you were the original sender of a message.
Establishing non-repudiation in cryptography can also be done using methods like digital signatures.
Why Is Cryptography Important?
Cryptography is one of the major pillars of our modern digital world and essential for usage of cryptocurrency.
It’s used to secure everything from online banking to digital currencies like Bitcoin and Ethereum.
It protects us, our livelihoods, and our global communications infrastructure from manipulation and attack by malicious actors.
Types of Cryptography
A few distinct types of cryptography exist based on their practical application.
Symmetric Cryptography
What is commonly referred to as symmetric cryptography is also known as private or private-key cryptography.
This approach relies on the distribution of a single description key among all parties wishing to communicate securely over an open channel. You can think of this key as a password, which can be used to decipher encrypted information (i.e., ciphertext). It also serves the purpose of alerting its users of data tampering.
The downside here is that all parties must keep one single key secure at all times.
Asymmetric Cryptography
Asymmetric cryptography (a.k.a. public or public-key cryptography) is a more popular and modern approach to encrypting data meant to be shared over open networks.
This is a dual-key approach that involves both private and public keys.
Here, both parties share a public key with each other. There is no need to protect this key from eavesdroppers and attackers as it alone can not be used to decrypt messages, only to encrypt them.
The message sender will use the message receiver’s public key to encrypt the message, knowing that only the receiver will be able to decrypt the message. They would do that using their own personal private key, which is only known to them, not even to the sender.
Hybrid Cryptography
This method is a combination of both asymmetric and symmetric cryptography. In this approach, asymmetric cryptography is used initially to secure the connection and then symmetric cryptography handles the bulk of the data encryption and decryption throughout the communication’s duration.
Conclusion
Without cryptography, our world would look nothing like it does today. Anything other than face-to-face communication would be incredibly difficult to do securely, stunting forces of progress like globalization, scientific discovery, and global security.
PGP Corporation. (2002). An introduction to cryptography (Version 8.0). PGP Corporation. Retrieved from
https://www.cs.unibo.it/babaoglu/courses/security/resources/documents/intro-to-crypto.pdf
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