Is the process of converting a plaintext to a ciphertext using a digital key?

BASICS IN CRYPTOGRAPHY AND SECURITY

Inhaltsverzeichnis Show

What is the process of converting a plaintext to a ciphertext using a digital key?
How to convert plaintext to ciphertext?
Is the process of using a secret key to convert plaintext into ciphertext?
What is plaintext and ciphertext and key?

Definitions:

Cryptography: Cryptography is the art or science encompassing the principles and methods of transforming message into one that is unintelligible, and retransforming that to its original form.

plaintext: The original intelligible message.

ciphertext: The transformed message.

cipher: An algorithm for transforming and intelligible message into one that is unintelligible by transposition and/or substitution methods.

Encryption: The process of converting plaintext to ciphertext using a cipher and a key.

Decryption: The process of converting ciphertext back to plaintext using a cipher and a key.

Cryptanalysis: Cryptoanlysis is the practice of analyzing and breaking cryptography. It is important that the cryptographic
algorithms one uses be resistant to cryptoanalysis. Also called codebreaking.

Cryptography: The study of both cryptography and cryptanalysis.

Authentication: The assurance of identity of originator of data.

Common security threats:

Identity interception - Somebody might steal your identity and use it as their own.
Masquerading - If you send your username and password in cleartext, somebody might grab it from the network.
Replay attack - Capturing a request and replaying it.
Data interception and manipulation
Repudiation
Denial of service

Approaches to security:

Link encryption: Each vulnerable communication link is equipped on both ends with an encryption device. It has the following disadvantages:

It is only effective only if all potential weak links from source to destination are secured.
It violates end-to-end argument.

End-to-end encryption: Data is encrypted only at the source node and decrypted at the destination node.

We cannot encrypt the header, so data is secure but the traffic pattern is not secure. Here traffic pattern refers to

Identities of partners
How frequently do two partners communicate.
Message patterns. Eg: length, time.

Solution:

Use a combination of both procedures.

Other layers at which security can be implemented:

Network layer encryption: Examples: IPSEC,VPN,SKIP

Transport layer security: Examples: SSL,PCT(Private communication technology).

Application layer security: Examples: Privacy enhanced mail, Pretty good privacy, SHTTP

Taxonomy of ciphers:

Monoalphabetic cipher: letters of the plaintext are mapped into unique letters.
Polyalphabetic cipher: Letters of the plaintext are mapped into ciphertext space depending on their position on the text.
Stream cipher: A key stream is generated and is used to encrypt data. Encryption/Decryption is done one symbol at a time.
Block cipher: Encryption/Decryption is done on fixed size blocks.

Cryptanalysis:

The art of breaking ciphers is known as cryptanalysis.
Methods of cryptanalysis:
Ciphertext-Only : The opponent possesses a string of cipher text y.
Known plaintext: The opponent possesses a string of plaintext x, and the corresponding ciphertext string y.
Chosen plaintext: The opponent can choose a plaintext string x and construct corresponding ciphertext string y : he has obtained access to encryption machinery.
Chosen ciphertext: The opponent has obtained access to decryption machinery. He can chose ciphertext string y and construct the corresponding plaintext string x.

Types of security:

There are two fundamentally different ways ciphers may be secure.
Undonditional security:
No matter how much computing power is available, the cipher cannot be broken.
Computational security:
It may one one of the following:
Given limited computing resources (e.g., time needed for calculations is greater than time of universe), the cipher cannot be broken.
Provide evidence of computational security by reducing the security of cryptosystem to some well-studied problem thought to be difficult (e.g, factoring). Such systems are called Provably secure.

To enhance privacy i.e to increase data confidentiality we use encryption techniques.

There are two types of modern cryptographic algorithms: public-key algorithm and secret-key algorithm.

What is the process of converting a plaintext to a ciphertext using a digital key?

Cryptography is the process of converting between readable text, called plaintext , and an unreadable form, called ciphertext . This occurs as follows: The sender converts the plaintext message to ciphertext. This part of the process is called encryption (sometimes encipherment ).

How to convert plaintext to ciphertext?

There are two primary ways in which a plain text can be modified to obtain cipher text: Substitution Technique and Transposition Technique..

Substitution Technique: Substitution technique involves the replacement of the letters by other letters and symbols. ... .

Transposition Technique:.

Is the process of using a secret key to convert plaintext into ciphertext?

Encryption is the method by which information is converted into secret code that hides the information's true meaning. The science of encrypting and decrypting information is called cryptography. In computing, unencrypted data is also known as plaintext, and encrypted data is called ciphertext.

What is plaintext and ciphertext and key?

Ciphertext is encrypted text transformed from plaintext using an encryption algorithm. Ciphertext can't be read until it has been converted into plaintext (decrypted) with a key. The decryption cipher is an algorithm that transforms the ciphertext back into plaintext.