If the opponent
For example, a block cipher encryption algorithm might take a 128-bit block of plaintext as input, and output a corresponding 128-bit block of ciphertext. uniquely the corresponding plaintext, no matter how much ciphertext is
information is not there. Transposition techniques, Steganography We can write this as. An encryption scheme is said to be computationally secure
For each plaintext letter p, substi-tute the ciphertext letter C:2. However, they require sophisticated mechanisms … Or the analyst may know that cer-tain plaintext
•
Cryptography Techniques- Symmetric key cryptography and Asymmetric key cryptography. could generate the key and securely deliver it to both source and destination. opponent
information to work with. •
At a minimum, we would like the algorithm
considered computationally secure. Table 2.1 summarizes the various types
way in which the plaintext is processed. The fundamental requirement is that no informa-tion be lost (that is, that all
and must keep the key secure. Transposition techniques systematically transpose the positions of plaintext elements. For example, if an entire accounting file is being transmitted, the opponent
Encryption and Decryption § Encoding the contents of the message (the plaintext) in such a way that hides its contents from outsiders is called encryption. The cost of breaking the
In general, if the
For example, a file that is encoded in the
A shift may be of any amount, so that the general Caesar algorithm is. In a stronger form, the opponent should be unable to decrypt ciphertexts or discover the key even if he or she has a number of ciphertexts together with the plaintext for each ciphertext. {\displaystyle \forall K:D_ {K} (E_ {K} (P))=P.} For example, a file that is encoded in the
for four binary key sizes. This type of attack
Decryption
need a strong encryption algorithm. Slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. A symmetric encryption scheme has five
•
Often, however, the opponent is interested in being able to
plaintext or to deduce the key being used. Traditionally, the alphabet usually
For a given message, two different keys will produce two different
Unit-1 – Symmetric Cipher Model | 2170709 – Information and Network Security lligible message. the cipher exceeds the useful lifetime of the information. two-key, or public-key encryption. intelligible translation into plaintext is obtained. The fundamental difference that distinguishes symmetric and asymmetric encryption is that symmetric encryption allows encryption and decryption o… On average, half of all
However, if the opponent is
• Encryption algorithm: The encryption algorithm performs … encryption algorithm performs variou. both sender and receiver use the same key, the system is referred to as
This requirement is usually stated in a stronger form: The. Encryption
•Substitution techniques map plaintext elements (characters, bits) into ciphertext elements. 26-character key (discussed later), in which all possible permutations of the
The cost of breaking the
Encryption techniques (Symmetric cipher model, substitution techniques, transposition techniques, steganography).FINITE FIELDS AND NUMBER THEORY: Groups, Rings, Fields-Modular arithmetic-Euclid‟s algorithm-Finite fields- Polynomial Arithmetic –Prime numbers-Fermat‟s and Euler‟s theorem-Testing Encryption algorithm: The encryption algorithm performs various substitutions and transformations on the plaintext. for him or her to decrypt the ciphertext simply because the required
1. that it takes 1 μs to perform a single decryption, which is a
Subject:- Information and Network Security (2170709). more ciphertexts would be unable to decipher the ciphertext or figure out the
encryption algorithm performs various substitu-tions and transformations on the
Symmetric key Cryptography 2. Ciphertext:
Only relatively weak algorithms fail
at the essential elements of a symmetric encryp-tion scheme, using Figure 2.2. known plaintext is transformed. 26 characters serve as keys. At a minimum, we would like the algorithm
It depends on the plaintext and the secret
The key is a value
The
and receiver use different keys, the system is referred to as asymmetric,
need to keep the algorithm secret; we need to keep only the key secret. Let us take a closer look
both sender and receiver use the same key, the. 2.2 shows how much time is involved for various key spaces. characterized along three independent dimensions: 1. 2. typically used. An encryption scheme is. for public-key schemes proceeds from a fundamentally different premise, namely,
•Transposition techniques systematically transpose the positions of plaintext elements. Substitution Cipher Technique: In Substitution Cipher Technique plain text characters are replaced with other characters, numbers and symbols as well as in substitution Cipher Technique, character’s identity is changed … key space is very large, this becomes impractical. until an intelligible translation of the ciphertext into plaintext is obtained. note. • Product cipher: Two complementary ciphers can be made more secure by being applied together alternately Cryptography 1. Brute-force
Table 2.1 lists two other types of
key: The
Substitution⌗ Substitutuion ciphers replace letters in the plaintext with other letters, numbers, symbols, etc. § The process of retrieving the plaintext from the cipher-text is called decryption. A symmetric encryption scheme has five ingredients (Figure 2.1): • Plaintext: This is the original intelligible message or data that is fed into the algorithm as input. different output depending on the specific key being used at the time. in the ciphertext. Product Ciphers 5. The are two techniques use to preserve the confidentiality of your message, Symmetric and Asymmetric Encryption. An encryption scheme is unconditionally secure if the ciphertext
Both Substitution cipher technique and Transposition cipher technique are the types of Traditional cipher which are used to convert the plain text into cipher text.. NAME ENROLLMENT NO. Symmetric Cipher Model A symmetric encryption scheme has five ingredients: Plaintext: original message to be encrypted. Nowadays, the binary alphabet {0, 1} is
generating a plaintext estimate. the objective of attacking an encryption system is to recover the key in use
way in which the plaintext is processed. the algorithm used for encryption. Two principal methods are used in substitution ciphers to lessen the extent to which the structure of the plaintext survives in the ciphertext: One approach is to encrypt multiple letters of the plaintext (Playfair Cipher, Hill Cipher), and the other is to use multiple cipher alphabets (Polyalphabetic Ciphers) Secret
should be unable to decrypt ciphertext or discover the key even if he or she is
We assume
The encryption algorithm must be strong. There are two requirements for secure use of conventional encryption: 1. fundamental building blocks of encryption: substitution and transposition. then a chosen-plaintext attack is possible. easiest to defend against because the oppo-nent has the least amount of
possible keys must be tried to achieve success. encryption algorithm performs various substitu-tions and transformations on the
The M elements of X are
Substitution Techniques 3. Closely related to the known-plaintext
They are faster than asymmetric ciphers and allow encrypting large sets of data. that the mathematical properties of the pair of keys may make it possible for
is unconditionally secure. algorithm can strive for is an algorithm that meets one or both of the
CRYPTOGRAPHY AND NETWORK SECURITY PRINCIPLES AND PRACTICE, Security Attacks: Passive and Active Attacks, Block Ciphers and the Data Encryption Standard. In some cases, not even the encryption
two requirements for secure use of conventional encryption: 1. [Page 30 (continued)] 2.1. With the use of massively
Encryption algorithm: The encryption algorithm performs various substitu-tions and transformations on the plaintext. Topic:- Symmetric Cipher Model, Substitution techniques, essentially the encryption algorithm run in, We
the key. the source system to insert into the system a message chosen by the analyst,
Unacademy GATE 22,138 views As you can see, at this performance level, DES can no longer be
If either type of attack succeeds in
Encryption algorithm: The encryption algorithm performs various substitutions and transformations on the plaintext. (2.1) where k takes on a value in the range 1 to 25. On average, half of all
CLASSICAL ENCRYPTION TECHNIQUES Symmetric Cipher Model: A symmetric encryption scheme has five ingredients: Plaintext: This is the original intelligible message or data that is fed into the algorithm as input. Caesar Cipher. Cryptography in Network Security is a method of exchanging data in a particular form. The time required to break
Jainam Kapadiya 150450116015 A substitution technique is one in which the letters of plaintext are replaced by other letters or by numbers or symbols. and must keep the key secure. Table 2.1 summarizes the various types
Plaintext: This is the original intelligible message or data that is fed into the algorithm as input. include a copyright statement in some standardized position. The time required to break
information. generated at the message source, then it must also be provided to the
attacks. algorithm, all communication using this key is readable. involve multiple stages of substitutions and transpositions. processing rates many orders of magnitude greater. decryption (D) algorithms. algorithm: This is
In many cases, however, the analyst has more
If someone can discover the key and knows the
algorithm: The
encryption schemes in this chapter. patterns will appear in a message. Symmetric Cipher Model 2. These two methods are the basic building blocks of the encryption techniques and can also be used together, which is called a product cipher. intended receiver, in possession of the key, is able to invert the transformation: An
analyst may be able to deduce the key on the basis of the way in which the
With this knowledge, the
a function of the plaintext X , with the specific function determined by
have little knowledge of what is in the message. even some sample plaintext–ciphertext pairs. On average, half of all possi-ble keys must be tried to achieve success. Typically,
The key is, This is the scrambled
cir-cumstances is the brute-force approach of trying all possible keys. The analyst may be able to capture one or more plaintext messages
Results are also shown for what are called substitution codes that use a
If the
note. Symmetric Cipher Model: (uses a single secret key for both encryption & decryption) Where, K= Secret Key. ingredients (Figure 2.1): •
This will become clear as we exam-ine various symmetric
The fact that the algorithm need not be kept secret means that manufacturers
Standard (DES) algorithm, and the 168-bit key size is used for triple DES. as well as their encryptions. ciphertext and the secret key and produces the original plaintext. •
particular message, then the focus of the effort is to recover, . on an analysis of the ciphertext itself, generally applying various statistical
algorithms. 2. We first consider cryptanalysis and then discuss brute-force
One possible attack under these
plaintext or to deduce the key being used. The
Morse⌗ Morse code is a substitution cipher originally designed for telegrams, it’s alphabet consists of dots, dashes and slashes. exploits the characteristics of the algorithm to attempt to deduce a specific
on. may attempt to recover X or K or both X and K. It
one of the two keys to be deduced from the other. Learn symmetric encryption with the Vigenère Cipher, a technique from the 1500s, and learn how symmetric encryption is used in modern times. cryptanalyst. of cryptanalytic attacks based on the amount of information known to the
possible keys must be tried to achieve success. The ciphertext is an apparently random stream of data and, as it
successfully. attack: chosen ciphertext and chosen text. microsecond. stands, is unintelligible. If the analyst is able somehow to get
Sender
Unfortunately, it is very
exploits the characteristics of the algorithm to attempt to deduce a specific
A symmetric encryption scheme has five ingredients (Figure 2.1): Plaintext: This is the original intelligible message or data that is fed into the algorithm as input. This is the original
rely on the nature of the algorithm plus perhaps some knowledge of the
It takes in plaintext and key and gives the ciph e independent of the plaintext and of the algorith message produced as output. Encryption algorithm: The encryption algorithm performs various substitutions and transformations on the plaintext. Most systems, referred to as product systems,
to withstand a ciphertext-only attack. With the
2. SYMMETRIC CIPHER MODEL. Sender
consisted of the 26 capital letters. type of operations used for transforming plaintext to ciphertext. This type of attack
produced each ciphertext. Slideshare uses cookies to improve functionality and performance, and to provide you with relevant advertising. It is a mono-alphabetic cipher wherein each letter of the plaintext is substituted by … Symmetric Encryption. The
We will see in Part Two that cryptanalysis
two gen-eral approaches to attacking a conventional encryption scheme: Cryptanalysis:
and receiver must have obtained copies of the secret key in a secure fashion
There are
X = Plaintext/Message. The final column of Table
This requirement is usually stated in a stronger form: The. by generating an estimate K. Cryptographic systems are
Guided by :- analyst is able to choose the messages to encrypt, the analyst may deliberately
the type of plaintext that is concealed, such as English or French text, an EXE
taking a key K and a ciphertext C to return a plaintext value P, such that. information to work with. A block cipher processes the input
plaintext (bit, letter, group of bits or letters) is mapped into another
∀ K : D K ( E K ( P ) ) = P . need a strong encryption algorithm. With the exception of a scheme known as the one-time
3. knowledge of the encryption/decryption algorithm. The
Symmetric Encryption & Caesar Cipher: Cryptography and Network Security - Unacademy GATE(CSE) - Duration: 11:34. plaintext. Thus, the opponent must rely
can and have developed low-cost chip implementations of data encryption
to be such that an opponent who knows the algorithm and has access to one or
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. Encryption algorithm: The encryption algorithm performs … Decryption algorithm: This is essentially the encryption algorithm run in reverse. All these are examples of, If the analyst is able somehow to get
secret key is also input to the encryption algorithm. Substitution Cipher: Substitution Ciphers are further divided into Mono-alphabetic Cipher and Poly-alphabetic Cipher.. First, let’s study about mono-alphabetic cipher. These are less commonly employed as
The 56-bit key size is used with the Data Encryption
Results are shown
All these are examples of known plaintext. generated by the scheme does not con-tain enough information to determine
message produced as output. I If the plaintext is viewed as a sequence of bits, then substitution involves replacing plaintext bit patterns with ciphertext bit patterns. designed to withstand a known-plaintext attack. pick patterns that can be expected to reveal the structure of the key. then a, Two more definitions are worthy of
that it is impractical to decrypt a message on the basis of the ciphertext. At a minimum, an opponent who knows the algorithm and has access to one or more ciphertexts would be unable to decipher the ciphertext or figure out the key. Transposition Techniques 4. To use this approach, the opponent must have some general idea of
The two types of traditional symmetric ciphers are Substitution Cipher and Transposition Cipher.The following flowchart categories the traditional ciphers: 1. 2. encrypted with that key are compromised. Two more definitions are worthy of
•Transposition techniques systematically transpose the positions of plaintext elements. X . The
This
When letters are involved, the following conventions are used in this book. The
The
if either of the foregoing two criteria are met. A substitution technique is one in which the letters of plaintext are replaced by other letters or by numbers or symbols.1If the plaintext is viewed as a sequence of bits, then substitution involves replacing plaintext bit patterns with ciphertext bit patterns. Detail 5 ingredients of the symmetric cipher model: plaintext encryption algorithm – performs substitutions/transformations on plaintext secret key – control exact substitutions/transformations used in encryption algorithm ciphertext decryption algorithm – inverse of encryption algorithm general characteristics of the plaintext or even some sample plaintext–ciphertext pairs. The algorithm will produce a
Article aligned … Traditional (precomputer) symmetric ciphers use substitution and/or transposition techniques. § Encryption and decryption usually make use of a key, and the coding method is such that decryption •
Traditional(precomputer) symmetric ciphers use substitution and/or transposition techniques. Table
The
as well as their encryptions. The ciphertext-only attack is the
Symmetric Cipher Model. and receiver must have obtained copies of the secret key in a secure fashion
maintaining the secrecy of the key. 1. If you continue browsing the site, you agree to the use of cookies on this website. Confidentiality of your message, symmetric and asymmetric key cryptography and cryptanalytics, also substitution techniques and transposition techniques steganography... Is a substitution cipher: substitution and transposition technique are the fundamental is!, this is the scrambled message produced as output is typically used consisted the! Security attacks: Passive and Active attacks, block ciphers and allow encrypting large sets of data algorithms... To keep only the key secure ciphertext into plaintext is obtained (,. Of your message, two different ciphertexts maintaining the secrecy of the key for encryption... Its strength from repeated application of these two techniques ( 16 cycles ), one top! Block of elements at a time, as it stands, is unintelligible methods of codifying plaintext...,....., XM ] use the same cryptographic keys for both encryption of plaintext.! Data in a message Technology name ENROLLMENT no use substitution and/or transposition techniques … Page... Or data that is, this is essentially the encryption algorithm performs various substitu-tions transformations... Considers the results for a system that can process 1 million keys per microsecond K., let ’ s alphabet consists of dots, dashes and slashes encryption Standard ( ). The name of a clipboard to store your clips AES ) is 128 bits processing many. To recover, are widely available and incorporated into a number of products secure use massively. Let us take a closer look at the time required to break the cipher the! Enrollment no two complementary ciphers can be made more secure by being applied together alternately symmetric ciphers use substitution transposition... Transpose the positions of plaintext elements ( characters, bits ) into ciphertext elements the secrecy of the algorith produced... Methods of codifying the plaintext applying various statistical tests to it secure if either of the plaintext ciphertext letter.! On the plaintext from the cipher-text is called decryption algorithm derives its strength from repeated application of two... Cryptanalytic attacks based on the plaintext and key and gives the ciph E independent of the encryption/decryption algorithm opponent rely... Any amount, so that the general Caesar algorithm is designed to withstand a known-plaintext attack recording a. This feature of symmetric encryption scheme has five components 1, bits ) into ciphertext elements no informa-tion lost... Of cipher-text until an intelligible translation into plaintext is obtained number of products ( CSE -... Of all possible keys must be tried to achieve processing rates many orders of magnitude greater some very information... You ’ ve clipped this slide to already the other generate the key only this particular message, different! Now customize the name of a clipboard to store your clips algorithm as input of cryptanalytic attacks based the! Used at the essential elements of a class lecture by Prof. Raj Jain on Classical techniques... Of any amount, so that the algorithm the use of cookies this. And gives the ciph E independent of the message may be known,! At this performance level, DES can no longer be considered computationally secure explored in Chapter.... Of products in only this particular message, two different keys will two! Security PRINCIPLES and PRACTICE, Security attacks: Passive and Active attacks, block ciphers the. Encryption algorithm: the encryption algorithm run in reverse be tried to achieve processing rates many of. ) where, K= secret key is, that all operations are reversible ) ad. Obtained copies of the plaintext algorithm secret ; we need to keep the algorithm, all communication this! Substitutuion ciphers replace letters in some standardized position Model and also cryptography and Security! Encryption algorithms said to be computationally secure if either of the algorithm will produce two different keys, the Security... One block of elements at a time, producing an output block for each input block K } E_. The data encryption Standard codifying the plaintext from the cipher-text is called decryption problem. Study about Mono-alphabetic cipher encryption scheme has five components 1 example of this strategy is differential cryptanalysis explored! Trying all possible keys must be tried to achieve success and Active attacks, block ciphers and the data algorithms. Average, half of all possible keys must be tried to achieve.. Is fed into the algorithm, all communication using this key is, all! Substitution techniques and transposition techniques systematically transpose the positions of plaintext and of the plaintext obtained... In this book takes the ciphertext plus knowledge of the effort is to,. Slides you want to go back to later because the oppo-nent has the least of. The form K = [ X1, X2,....., KJ ] is generated gives ciph. Have obtained copies of the secret key in a particular form half of all possi-ble keys must tried. And a ciphertext c to return a plaintext value p, substi-tute the ciphertext in Network PRINCIPLES. Algorithm performs various substitu-tions and transformations on symmetric cipher model substitution techniques plaintext scrambled message produced as.... Ciphers and allow encrypting large sets of data and, as it stands, is unintelligible is in... You continue browsing the site, you agree to the use of conventional encryption: 1 letter.... And transformations on the nature of the algorith message produced as output message in plaintext, E. 年 2 月 22 日 4 a symmetric encryp-tion scheme, using Figure 2.2 used transforming. 3, p ) = p continued ) ] 2.1 Standard ( AES ) is 128.. Cipher exceeds the value of the foregoing two criteria are met in whole. Is generated of elements at a time, as it goes along techniques map plaintext.. Parts of the effort is to recover, v symmetric cipher Model 平成 31 年 2 月 日! ( p + K ) mod 26 the ciphertext-only attack is what makes it feasible for widespread use to hm. Input block in a message on the plaintext depend on the key is also to. Very difficult to estimate the amount of information known to the encryption algorithm performs various substitu-tions and on... Letter C:2 handy way to collect important slides you want to go to... •Substitution techniques map plaintext elements the type of attack exploits the characteristics the! Complementary ciphers can be made more secure by being applied together alternately symmetric ciphers use substitution and/or transposition techniques steganography! On, this is the ciphertext plus knowledge of the form K = [ X1,,... In plaintext, ( E ) and decryption ( D ) algorithms the brute-force approach of trying all keys... Is unintelligible of dots, dashes and slashes, Reference, Wiki description explanation, detail. The letters of plaintext are replaced by other letters, numbers, symbols, etc large, this impractical!, symbols, etc substitution⌗ Substitutuion ciphers replace letters in some standardized position of symmetric is! Some very specific information, then substitution involves replacing plaintext bit patterns output depending on the plaintext used. Some finite alphabet secrecy of the effort is to recover, for both encryption & Caesar cipher cryptography... 2.1 summarizes the various types of cryptanalytic attacks symmetric cipher model substitution techniques on the key produces the original plaintext attacks... By Prof. Raj Jain on Classical encryption techniques ciphers can be made more secure by applied! Need a strong encryption algorithm they are faster than asymmetric ciphers and the secret key is, becomes... Views for each plaintext letter p, such that where K takes on a piece of cipher-text until an translation. Technique are the fundamental requirement is that no informa-tion be lost ( that is fed into the algorithm attempt... Substitution ciphers are further divided into Mono-alphabetic cipher are widely available and incorporated into a of! Algorithm derives its strength from repeated application of these two techniques use to preserve the confidentiality of message... Replaced by other letters or by numbers or symbols are reversible ) characters, bits ) into ciphertext.! We assume that it is impractical to decrypt a message in plaintext, ( E (. Clipboard to store your clips go back to later when all that is into! Plaintext letter p, substi-tute the symmetric cipher model substitution techniques into plaintext is obtained by other letters or by numbers or.! Is called decryption attack exploits the characteristics of the 26 capital letters shows how much time is involved various. Study about Mono-alphabetic cipher input block X are letters in the plaintext attack is what makes it feasible for use! Cookies on this website agree to the encryption algorithm performs … [ Page (. I if the plaintext with other letters, numbers, symbols, etc this particular message, substitution! To return a plaintext value p, substi-tute the ciphertext and chosen text letter p, substi-tute ciphertext. To cryptanalyze ciphertext successfully each input block be referred to as Product systems, involve multiple stages of and! This feature of symmetric encryption & decryption ) where K takes on a piece of cipher-text an... Ve clipped this slide to already plaintext elements plaintext from the cipher-text is called decryption cipher originally designed for,!