Cryptography MCQ Free PDF Objective Question Answer for Cryptography Quiz Download Now!

Decryption is thus the reverse process, which involves decrypting the current ciphertext and then adding the previous ciphertext block to the result. IDEA − It is a sufficiently strong block cipher with a block size of 64 and a key size of 128 bits. A number of applications use IDEA encryption, including early versions of Pretty Good Privacy protocol. The use of IDEA scheme has a restricted adoption due to patent issues. The length of plaintexts is mostly not a multiple of the block size. For example, a 150-bit plaintext provides two blocks of 64 bits each with third block of balance 22 bits.

Cryptography Objectives

In many digital communications, it is desirable to exchange an encrypted messages than plaintext to achieve confidentiality. In public key encryption scheme, a public key of sender is available in open domain, and hence anyone can spoof his identity and send any encrypted message to the receiver. The previous modules explained the characteristics, strengths, and uses of cryptographic algorithms. As a security professional, we will use these algorithms in many ways including secure email, virtual private networks , e-commerce and wireless security. Most cryptographic systems use a combination of symmetric and asymmetric algorithms, hashing, and digital signatures.

Cryptography Introduction

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. OpenSSL is an opensource project that provides a cryptography library and tools for use on a variety of platforms. GnuTLS is an opensource project that provides a cryptographic library for use on a variety of platforms, including Linux, Windows, and Mac. Get in touch with our team at Triskele Labs and discover how we can help you protect your data and integrate cryptography into your security strategies and systems.

Cryptography Objectives

Also, padding may render the system insecure at times, if the padding is done with same bits always. An example is a ‘simple columnar transposition’ cipher where the plaintext is written horizontally with a certain alphabet width. It is another type of cipher where the order of the alphabets in the plaintext is rearranged to create the ciphertext. Here, each plaintext character has been shifted by a different amount – and that amount is determined by the key.

Cryptography Fundamentals – Part 1

It is a slower but has more secure design than other block cipher. Known Plaintext Attack − In this method, the attacker knows the plaintext for some parts of the ciphertext. The task is to decrypt the rest of the ciphertext using this information. This may be done by determining the key or via some other method. The best example of this attack is linear cryptanalysis against block ciphers. Length of Keys in this encryption is large and hence, the process of encryption-decryption is slower than symmetric key encryption.

In this scheme, the plaintext is processed one bit at a time i.e. one bit of plaintext is taken, and a series of operations is performed on it to generate one bit of ciphertext. Technically, stream ciphers are block ciphers with a block size of one bit. Ciphertext Only Attacks − In this method, the attacker has access to a set of ciphertext. COA is said to be successful when the corresponding plaintext can be determined from a given set of ciphertext.

Cryptography Objectives

The ECB mode is deterministic, that is, if plaintext block P1, P2,…, Pm are encrypted twice under the same key, the output ciphertext blocks will be the same. The number of rounds used in a Feistel Cipher depends on desired security from the system. But at the same time, more rounds mean the inefficient slow encryption and decryption processes. 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.

Padding in Block Cipher

In this mini-course, we will learn about various aspects of cryptography. We’ll start with cryptography objectives, the need for it, various types of cryptography, PKI, and we’ll look at some practical usage in our daily digital communication. In this mini-course, I will explain every detail with an example which end users can perform on their machines. The steps of sending a message through a public-key encryption. If the keystream is random, this scheme would be unbreakable unless the keystream was acquired, making it unconditionally secure.

In steganography, an unintended recipient or an intruder is unaware of the fact that observed data contains hidden information. In cryptography, an intruder is normally aware that data is being communicated, because they can see the coded/scrambled message. The first known evidence of cryptography can be traced to the use of ‘hieroglyph’. Some 4000 years ago, the Egyptians used to communicate by messages written in hieroglyph. This code was the secret known only to the scribes who used to transmit messages on behalf of the kings. The art of cryptography is considered to be born along with the art of writing.

Integrity gives the assurance that the information received is exact and accurate. 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. This module defines the technical terms in cryptography and introduce Alice, Bob, and Eve. We will also describe Security by Obscurity, which contrasts Kerckhoff’s Principle. This cryptography project is a type of public-key cryptography that uses elliptic curves to generate keys. These cryptography projects may be sponsored by governments or other organizations that have a need to eavesdrop on communications or tamper with data.

With 26 letters in alphabet, the possible permutations are 26! The sender and the receiver may choose any one of these possible permutation as a ciphertext alphabet. Man in Middle Attack − The targets of this attack are mostly public key cryptosystems where key exchange is involved before communication takes place. In a public-key cryptosystem, the encryption key is in open domain and is known to any potential attacker. Using this key, he can generate pairs of corresponding plaintexts and ciphertexts.

Waxed seals and ciphers were used to send secret messages throughout history and in almost every culture. Encrypted messages were sent by spies, in the military, and between diplomats during times of war and conflict. Now, cryptography has changed drastically with the advances in technology.

  • Addition of cryptographic techniques in the information processing leads to delay.
  • Confidentiality gets compromised if an unauthorized person is able to access a message.
  • The hash function generates a hash code by operating on two blocks of fixed-length binary data.
  • In a public-key cryptosystem, the encryption key is in open domain and is known to any potential attacker.
  • This principle ensures that the sender cannot deny the fact that he/she sent the data.
  • Attacks are typically categorized based on the action performed by the attacker.

One is used for encryption, while the other key can decrypts the message. Unlike symmetric cryptography, if one key is used to encrypt, that same key cannot decrypt the message, rather the other key shall be used. Stream cipherBlock ciphers — process messages in blocks, each of which is then encrypted or decrypted.

Security Value

Non-repudiation – cryptography provides traceability of the message to make sure it is legitimate. Messages are traced and the system verifies they were sent and received so neither person can deny their validity. Authentication and Identification – in order to maintain the security of the information, the identities of the sender and receiver are verified and authenticated. Communication does not happen until authentication has taken place. Confidentiality – the information being sent and received should not be seen by anyone other than the intended recipients. Cryptography strives to maintain the secrecy of its key so that, even if a third party were to intercept the message, it could not be deciphered.

This is a property which set this scheme different than symmetric encryption scheme. The ciphertext block is XORed with the output of encrypted contents of counter value. After decryption of each ciphertext block counter is updated as in case of encryption. Apparently, CFB mode is converting a block cipher into a type of stream cipher. The encryption algorithm is used as a key-stream generator to produce key-stream that is placed in the bottom register.

Cryptography Objectives

Encryption, therefore, is the only way to ensure that your information remains secure while it’s stored and being transmitted. Compare your organization’s encryption strategy with the global firm’s how does cryptography work trend and understand the data protection strategies across multi-dimensional platform analysis. — The size of the enciphered text should be no larger than the text of the original message.


Cell phones, internet sites , and banking are just three of the many common uses of cryptography to keep your information secure. Integrity – it is vitally important that the information being transmitted stays in its original form. Nothing about the message should be modified or tampered with in any way. Part of the cryptography system ensures that any information sent or received is not altered. Usually implemented as a stream cipher using the XOR function.

Goals of Cryptography

The decryption key is related to the encryption key, but is not always identical to it. The receiver inputs the decryption key into the decryption algorithm along with the ciphertext in order to compute the plaintext. It refers to the design of mechanisms based on mathematical algorithms that provide fundamental information security services.

Elliptic Curve Cryptography has already been invented but its advantages and disadvantages are not yet fully understood. ECC allows to perform encryption and decryption in a drastically lesser time, thus allowing a higher amount of data to be passed with equal security. However, as other methods of encryption, ECC must also be tested and proven secure before it is accepted for governmental, commercial, and private use.

With innovations and advancements, cryptography has the potential to propel the world to new heights. Authentication is the process of making sure that the piece of data being claimed by the user belongs to it. At the end, LPT and RPT are re-joined and a final permutation is performed on combined block. Large changes in cipher text when the keyword is changed minimally is what avalanche effect is about. Finally, the message is read off in columns, in the order specified by the keyword. Width of the rows and the permutation of the columns are usually defined by the keyword.

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