What is Cryptology? What are its types?

The invention of the computer, along with the spread of technology and internet usage, transformed human communication into electronic communication. Consequently, the concept of security has gained great importance in electronic communication environments.

Cryptology is an interdisciplinary, mathematics-based field related to computer science that ensures data security in electronic communication. It studies the reliability of cryptographic devices and the algorithms used within them.

Cryptology focuses on essential objectives such as privacy, authenticity, and integrity of messages while encrypting their content.

It should also be noted that in cryptology, even if different ciphers are used each time, repeatedly applying the same method will eventually lead to its discovery. Therefore, some fundamental principles were established. One of them is:
“A cryptographic system should remain secure even if everything about it is known, except the encryption key.”

The most effective way to realize this principle is by using randomly generated secret keys. For this reason, all modern cryptographic systems are built upon secret keys.

Applications of Cryptology

• Email encryption
• Instant messaging
• Online banking
• Credit card security
• Blockchain and cryptocurrencies
• Government and military applications, encryption of classified documents and secure communication
• Data encryption
• Authentication
• VPN and proxy systems
• Electronic signature and digital identity
• Application security
• IoT security
• Protection of patient data in healthcare
• Data validation
• Online game security
• Licensing and DRM in the entertainment industry

In short, whenever communication takes place in an electronic environment, cryptology is present. 😊

The Two Main Branches of Cryptology

• Cryptography (encryption)
• Cryptanalysis (decryption)

It also includes hash functions, block ciphers, and quantum cryptology.

Additionally, cryptology has several subfields:

• Classical (symbolic) encryption
• Symmetric encryption
• Asymmetric encryption
• Hash functions
• Quantum cryptology

In this article, to explain the logic of cryptology in an understandable way, we will cover cryptography, cryptanalysis, symmetric encryption, and asymmetric encryption. If these topics interest you, further research into the other subfields would be beneficial.

What Is Cryptography?

• Cryptography refers to encryption techniques used to transmit information securely and privately.
• It is the science of creating encryption protocols regularly to protect data. In general, we can say cryptography represents the encryption methods used within cryptology.
• Cryptographic protocols include:
• 128-bit or 256-bit encryption
• Secure Sockets Layer (SSL) and Transport Layer Security (TLS)
• These protocols protect all kinds of digital information and data, from passwords and emails to e-commerce and banking transactions.
• Cryptography includes two main techniques: symmetric (shared-key) encryption and asymmetric (public-key) encryption.
• Symmetric Encryption
• The simplest and most widely used encryption method.
• Uses a single key for encryption and decryption.
• Advantages: Fast processing.
• Disadvantages: The need for a shared key.
• Examples of symmetric encryption algorithms: AES, DES, 3DES, Blowfish, Twofish, RC family (Ron's Code).
• How it works:
• The sender and receiver share a secret key unknown to others.
• The key converts plain text into an unintelligible cipher text.
• To verify message integrity, a Message Authentication Code (MAC) is added. Even a small modification invalidates the MAC.

Disadvantages:

• Attackers may infer the plaintext length from the ciphertext length.
• Extra information about the communicating parties (e.g., who they are, their intent) may aid decryption.
• Asymmetric Encryption
• Also known as public-key encryption.
• Uses two keys: Public key and Private key.
• Advantages: Secure key exchange.
• Disadvantages: Slower than symmetric encryption.
• Examples of asymmetric algorithms: RSA, ECC, ElGamal, DSA (Digital Signature Algorithm), Diffie-Hellman.

How it works:

• The sender encrypts the message using the receiver’s public key.
• Only the receiver’s private key can decrypt it.
• For authentication, a digital signature (created with the sender’s private key) can be verified with the sender’s public key.
• Relies on prime factorization:
• Public key = large number
• Private key = prime factors of that number
• While public → private is extremely hard, private → public is straightforward.
• RSA encryption (most widely used):
• Public key encrypts, private key decrypts (and vice versa).
• RSA key lengths are typically 1024 or 2048 bits.
• Key generation considerations:
• Keys must not be predictable.
• Large numbers are usually used.
• Randomness is crucial: weak randomness = weak cryptosystem.

What Is Cryptanalysis?

• Cryptanalysis studies techniques for breaking ciphers and finding weaknesses in security systems.
• Two approaches to revealing plaintext:
• Decryption with a key (legitimate method).
• Analysis without a key (cryptanalysis), discovering patterns or weaknesses to reconstruct plaintext.
• The second approach, also known as codebreaking, employs various techniques.

With modern computing power, brute-force attacks (trying all possible keys) can also be used to break encrypted text, provided the encryption algorithm is known.