# Cryptography Basics The Objective Of Cryptography?

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RSA is probably the best known asymmetric encryption algorithm. Authentication is the mechanism to identify the user or system or the entity. It ensures the identity of the person trying to access the information. The authentication is mostly secured by using username and password. The authorized person whose identity is preregistered can prove his/her identity and can access the sensitive information. In present day scenario security of the system is the sole priority of any organisation.

Later in 1995, SHA-1 was designed to correct alleged weaknesses of SHA-0. A hash function is a mathematical function that converts a numerical input value into another compressed numerical value. The input to the hash function is of arbitrary length but output is always of fixed length. When sensitive information is exchanged, the receiver must have the assurance that the message has come intact from the intended sender and is not modified inadvertently or otherwise.

Number of rounds in the systems thus depend upon efficiency–security tradeoff. Serpent − A block cipher with a block size of 128 bits and key lengths of 128, 192, or 256 bits, which was also an AES competition finalist. It is a slower but has more secure design than other block cipher.

The concept of preventing data and communications by embracing codes to create a platform whose information is intended should have access to read and process it is called Cryptography. Here, the term ‘Crypt’ refers to ‘hidden/vault’, while the term ‘graph’ means ‘writing’. Cryptography is an application to achieve safe and secure information and communication processes from numerous suspicious and malicious third parties – adversaries. Here, encryption and a key are chosen to transfigure an input – plaintext into an output – ciphertext that is encrypted.

## Vigenere Cipher

It is a mono-alphabetic cipher wherein each letter of the plaintext is substituted by another letter to form the ciphertext. Unlike modern systems which are digital and treat data as binary numbers, the earlier systems worked on alphabets as basic element. Dictionary Attack − This attack has many variants, all of which involve compiling a ‘dictionary’. In simplest method of this attack, attacker builds a dictionary of ciphertexts and corresponding plaintexts that he has learnt over a period of time. In future, when an attacker gets the ciphertext, he refers the dictionary to find the corresponding plaintext. The attacker influences the sender to convert plaintext of his choice and obtains the ciphertext.

Encryption Function − It is considered as a one-way function of converting plaintext into ciphertext and it can be reversed only with the knowledge of private key d. Once the key pair has been generated, the process of encryption and decryption are relatively straightforward and computationally easy. Each receiver possesses a unique decryption key, generally referred to as his private key. It is worth mentioning that CBC mode forms the basis for a well-known data origin authentication mechanism.

This number which is between 0 and 25 becomes the key of encryption. The attacks on cryptosystems described here are highly academic, as majority of them come from the academic community. In fact, many academic attacks involve quite unrealistic assumptions about environment as well as the capabilities of the attacker. For example, in chosen-ciphertext attack, the attacker requires an impractical number of deliberately chosen plaintext-ciphertext pairs. In modern era, cryptography needs to cater to users who are connected to the Internet. In such cases, using a secret algorithm is not feasible, hence Kerckhoff principles became essential guidelines for designing algorithms in modern cryptography.

It is now considered as a ‘broken’ block cipher, due primarily to its small key size. The number of rows is obtained by dividing number of total ciphertext alphabets by key value and rounding of the quotient to next integer value. It is another type of cipher where the order of the alphabets in the plaintext is rearranged to create the ciphertext.

## Public Key Cryptography

— If ciphertext and plaintext are known, it should be computationally infeasible to determine the deciphering algorithm. Stream Ciphers — Message is broken into characters or bits and enciphered with a key or keystream. — Key is used once and discarded by both sender https://xcritical.com/ and receiver. Length of the Key character stream is equal to the message length. An Act of scrambling the information with or without a secret key to hide actual information Which helps protect stored information and protect information in the transmission.

- Hence, it has become imperative to protect useful information from malicious activities such as attacks.
- Session keys offer the advantages of symmetric encryption, speed, strength and simplicity, and, with key exchanges possible via digital methods, significant levels of automated security.
- Cryptology is the discipline of cryptography and cryptanalysis combined.
- The authorized person whose identity is preregistered can prove his/her identity and can access the sensitive information.
- This module defines the technical terms in cryptography and introduce Alice, Bob, and Eve.
- This usually involves a username and a password, but can also include other methods like a smart card, retina scan, voice recognition, or fingerprint scan.

Interestingly, the different modes result in different properties being achieved which add to the security of the underlying block cipher. It comprises of a series of linked operations, some of which involve replacing inputs by specific outputs and others involve shuffling bits around . The speed of exhaustive key searches against DES after 1990 began to cause discomfort amongst users of DES. There have been no significant cryptanalytic attacks on DES other than exhaustive key search.

Vigenere Cipher was designed by tweaking the standard Caesar cipher to reduce the effectiveness of cryptanalysis on the ciphertext and make a cryptosystem more robust. It is significantly more secure than a regular Caesar Cipher. Polyalphabetic Cipher is a substitution cipher in which the cipher alphabet for the plain alphabet may be different at different places during the encryption process. The next two examples, playfair and Vigenere Cipher are polyalphabetic ciphers. These earlier cryptographic systems are also referred to as Ciphers. In general, a cipher is simply just a set of steps for performing both an encryption, and the corresponding decryption.

## Cryptography And Network Security Principles

Another type of threat that exist for data is the lack of message authentication. In this threat, the user is not sure about the originator of the message. Message authentication can be provided using the cryptographic techniques that use secret keys as done in case of encryption.

In this post, we explore what these reveal about cryptography. Cryptography is an information security tactic used to protect enterprise information and communication from cyber threats through the use of codes. At Triskele Labs, we consider it the art of hiding information to prevent unauthorised access to your data.

Data-in-use is still data that requires protection, and in modern secure systems, this data can be encrypted. The reason for more advanced cryptography methods is due to the need for data to be protected more and more securely. Most of the ciphers and algorithms used in the early days of cryptography have been deciphered, making them useless for data protection.

These two needs gave rise to the art of coding the messages in such a way that only the intended people could have access to the information. Unauthorized people could not extract any information, even if the scrambled messages fell in their hand. There are times where information needs to be obfuscated, protected from causal observation. In the case of a program, obfuscation can protect the code from observation by unauthorized parties. It is common for computer programs to have variable and function names changed to random names masking their use. Some people will write down things like PIN codes, but change the order of the digits so it is not immediately obvious.

## Block Size

In some cases the sender sends the message and later denies it. But the non-repudiation does not allow the sender to refuse the receiver. Integrity gives the assurance that the information received is exact and accurate.

The receiver now checks equality of freshly computed MAC with the MAC received from the sender. If they match, then the receiver accepts the message and assures himself that the message has been sent by the intended sender. At higher level of threat, attacker may modify data and try to derive new digest for modified data from exiting digest. This is possible if the digest is computed using simple mechanisms such as CRC. These data errors are likely to occur due to noise in a communication channel.

Digital signature is attached to an electronically transmitted document to verify its contents and the sender’s identity. It ensures the integrity, non-repudiation and authenticity of the message. Message digest is a hash value which is generated by applying a function on it. RSA algorithm (Rivest-Shamir-Adleman) is an algorithm used by modern technologies to encrypt and decrypt messages. The Data Encryption Standard is a symmetric-key algorithm for the encryption of digital data. In a symmetric key cryptographic system, both parties have access to the key.

## What Is Cryptography?

ElGamal cryptosystem, called Elliptic Curve Variant, is based on the Discrete Logarithm Problem. The serious disadvantage of CTR mode is that it requires a synchronous counter at sender and receiver. Loss of synchronization leads to incorrect recovery of plaintext.

## Challenge Of Public Key Cryptosystem

If the content of the message is changed after the sender sends it but before reaching the intended receiver, then it is said that the integrity of the message is lost. CryptoJS is an opensource project that provides a cryptography library for use on a variety of platforms. Crypto++ is an opensource project that provides a cryptography library for use on a variety of platforms. Bouncy Castle is an opensource project that provides a cryptography library for use on a variety of platforms.

Completeness − Each bit of ciphertext depends on many bits of plaintext. The DES satisfies both the desired properties of block cipher. Once the last round is completed then the two sub blocks, ‘R’ and ‘L’ are concatenated in this order to form the ciphertext block.

Those keys were generated when your system was first installed. In this exercise you will learn how to create host type keys for your server. Forward security is provided through a Diffie-Hellman key agreement.

Triple DES − It is a variant scheme based on repeated DES applications. It is still a respected block ciphers but inefficient compared to the new faster block ciphers available. Underneath the natural order alphabets, write out the chosen permutation of the letters of the alphabet. For encryption, sender replaces each plaintext letters by substituting the permutation letter that is directly beneath it in the table.

## Kerckhoffs Principle For Cryptosystem

For example, file servers often provide a pre-computed MD5 checksum for the files, so that a user can compare the checksum of the downloaded file to it. MD5 was most popular and widely used hash function for quite some years. Avalanche effect results in substantially different hash values for two messages that differ by even a single bit of data. Also, if a hash function is collision-resistant then it is second pre-image resistant. This property makes it very difficult for an attacker to find two input values with the same hash.

## Process Of Playfair Cipher

Individuals’ right to access personal information is referred to as privacy. There are a wide variety of cryptography projects available, each with its own strengths and weaknesses. In addition, Ethereum uses cryptography to power its smart contract functionality. What Is Cryptography Ethereum, another popular cryptocurrency, also uses cryptography to secure transactions. Bitcoin, the first and most well-known cryptocurrency, uses cryptography to secure transactions and to control the creation of new units of currency.