Domen Zavrl: What Is Cryptography?

Cryptography is a field of information security that is often misunderstood. Although the fundamental principles of algorithms generally stay the same, as infections and attacks evolve so too must these algorithms to maintain the security of confidential information.

Cryptography incorporates three key principles: encryption, integrity, and authentication.


To encrypt a file data is converted into an unreadable form, protecting its privacy during storage, transfer and reception. Encrypted data is decrypted via a process known as ‘decryption’.

In essence, encryption and decryption require a special key, so that while data appears scrambled, both the sender and the desired recipient can still read and understand it.


Cryptography assures message integrity, meaning that messages are accurately communicated and not altered or intercepted en route from the sender to the recipient. This is often achieved by hashing data, or cryptographically mapping out its path.

Maintaining message integrity requires technical skills. It can be accomplished using one of the following three techniques:

  1. Hash Functions.
  2. Public Key Cryptography.
  3. Secret Key Cryptography


Authentication is used to verify the sender’s identity. It consists of a short string of information that is used to confirm that the message originated from the stated sender. Method authentication code systems generally consist of three algorithms:

  • A key generation algorithm selecting a random key from the key space.
  • A signing algorithm that returns a tag containing the key and message.
  • A verifying algorithm that verifies the message’s authenticity by analysing the key and the tag. Messages that are accepted are not deemed forged or tampered with, whereas rejected messages are generally returned.

What Is the Difference Between Asymmetric and Symmetric Cryptography?

With asymmetric cryptography, two different keys are used to encrypt and decrypt the file. All participants in an asymmetric cryptosystem have both a public key and a private key. The public key can be freely distributed, but the private key is kept secret.

Data encrypted using a public key can only be decrypted using a corresponding private key.

With symmetric cryptography, both encryption and decryption are carried out using the same key. The sender and recipient must both already have the shared key.

Symmetric cryptography is generally more suitable for encrypting large amounts of data, since this form tends to be faster. Asymmetric cryptography is only suitable for encrypting files that are smaller than the size of the key, i.e. 2048 bits, or smaller.

Domen Zavrl has two PhDs: one in Applied Macroeconomics and the other in System Dynamics. Mr Zavrl has also studied Cryptology at Stanford University. He is an associate of Framingham Asset Management, as well as a member of The Institute of Internal Auditors.