What is Cryptography

Cryptography is essentially a means of protecting information with a cipher that can only be decrypted by the key. Its like having a key to your house, the key is distributed to the people you trust to have access.

How is Cryptography relevent to computers

I refer to this as Applied Cryptography. The main uses of applied cryptography is to protect computer data in a few key situations

  • Data At Rest: using Disk Encryption
  • Data In Transit: using Network Encryption like IPSEC, SSL, WPA
  • Data Access: Is a subset of data in transit & data at rest but focuses on controlling access to a network or device.

Why use Cryptography

In business, data should be encrypted both in transit and at rest on devices outside the organisation, eg laptops with work material in case they are lost or stolen, VPN provide cheap connectivity between remote workers and offices over the internet.

In the cloud, data should be encrypted both in transit and at rest. This protects your login identity and data from being stolen while on an untrusted server.

In banks, data is encrypted in transit to protect your money & investments from being stolen.

In social media like facebook, encryption is used to protect your login details from being snooped protect your reputation where someone could post deflaimation using your name. (just one example)

Encryption Concepts

Encrypt: convert plaintext into ciphertext

Decrypt: convert ciphertext back to plaintext

Plaintext: un-encrypted data, your document

Ciphertext: encrypted data, random un-distinguishable data

Cipher: create the ciphertext data according to a set pattern

Key: the random data that works with the cipher to create the ciphertext

Passcode: is the key to lock and unlock everything


I'm not a cryptographer, Im only interested in the secure implementation of software & procedures. Dont take my word for it, double check it yourself. This is a guide to learning and blog of my journey.