Basic Principles of Cryptography
I hope to explain some basic principals of cryptography world model and goals in this blog post. You can get an start on the Cryptography and the evaluation of Cryptography into modern state.
Secrets are a universal thing. A secret is not a problem until it retains within one person. What if we need to tell that secret to another person. Now we have to communicate with that person to tell the secret.
In this case, the biggest problem is how to do an end to end secure transfer of the secret. If we fail to do a secure communication then, that secret would not be a secret anymore. :/
The problem is the making sure Secure Communication. What is the solution?
Don’t worry. Cryptography solves this problem. If you are not familiar with Cryptography, please refer to my previous blog post, Getting started with Cryptography and key concepts… This blog post would help to get a start to the cryptography.
Cryptography is also a universal thing since the intention is to communicate the secrets which are a universal thing. Moreover, cryptography is not a modern concept, but it has a legendary history on its’ way to the present.
Problem : Secure communication between Alice and Bob.
Alice needs to send a secret to the Bob. But Eve can hear that secret. :(
Solution : Cryptographic Model
Alice can tell the secret in a concealed way that Eve cannot understand. There should be a secret key to get the actual secret of the transferring value. But that secret key is only with the Bob. Therefore, in this case, although Eve heard the transferring value, he can’t understand as he doesn’t have the secret key to get the actual secret. This model is called a Cryptographic model.
Kerckhoff’s principle on cryptography
Kerckhoff’s principle is the concept that a cryptographic system should be designed to be secure, even if all its details, except for the key, are publicly known.
After a message has been subjected to a cryptographic algorithm, it is expected to remain secure even if an intruder has or gains full access to the encrypted message and has knowledge of what algorithm was used. The point is that, even if a system’s design and details are not made open to begin with, they may be detected by an unauthorized party and, as such, should be inherently secure.
- Cryptographic Algorithm : primitive
- Cryptographic Protocol : How to use the primitives
In simple words, security only depends on the keys, not what happens at the ends. All the cryptographic algorithms are public.
Modern Primitives : Two families
To explain these two types, I am referring the same Alice and Bob’s story.
In this modern primitives, we use keys to encrypt and decrypt the message.
1. Symmetric Cryptography
- All keys are known by Alice and Bob.
- Either Alice or Bob can be interchanged as sender or reciever at any time as keys are not bind with the person.
2. Asymmetric Cryptography (Public Key Cryptography)
- Public keys and secret keys.
- Secret keys known only by owner.
- Bob and Alice use different keys.
- Simpler protocol, but primitives more difficult to design.
Hope this post would help you. Cheers :)
