What Is Encryption And Decryption Computer Science Essay

Encoding is transition of informations or kick text into a signifier, called cypher text.or transition of informations into unknown format ( scramble ) is known as encoding. Conversion of the cypher text into a field text or informations to a known format ( unscramble ) is known as decoding.

How Encryption works:

Encoding plan uses an encoding algorithm to code and decode the data.Encryption algorithm creates specific strings of informations used for encoding, keys that consists of long twine of spots or binary Numberss. The more spots in the key the more figure of possible combinations of binary Numberss that makes the codification more hard to interrupt.

Then encoding algorithm scrambles the information by cobining the spots in the key with the informations bits.In symmetric encoding the same key is used to scramble and unscramble the data.In asymmetric cardinal encoding two different keys needed, one for encoding and one for decoding.

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Why you need Encoding:

Nowadays more and more information is stored on computing machines and transmitted over the cyberspace, so we need to guarantee information security and safety.

One of the most common utilizations of encoding is coding electronic mails and directing sensitive messages, paperss and files over the cyberspace is like directing a post card as all electronic mails are transmitted in a unbarred signifier. It does n’t depend on if you send emails via public and private networks.your message is wholly unfastened to interception by anyone along the manner, so anybody your ISP, your brag etc.can read your electronic mails. Even if you connect to your waiter and direct electronic mails via SSL it merely means that your electronic mails ca n’t be seen while conveying between you and your server.when your electronic mail reaches your waiter it can be seen by your electronic mail service provider.then your waiter sends an electronic mail to the receiver in unbarred manner and your electronic mail besides be seen by anyone.

Private web where electronic mail straight goes to a mail waiter and resides at that place until it retrieved, besides does n’t supply necessary security degrees.ofcourse you believe that your personal electronic mail does n’t incorporate any private information, but everyone has got something to maintain secret from his household, neibours, friends.it could be fiscal, societal, political or professional secrets.There is certainly merely one manner to protect your privateness is – utilizing Encryption.

Encoding Footing:

The followers are the some of import encoding footings used in cryptanalysis,

Cryptanalysis: The art of concealing information utilizing encoding.

Cryptanalyst: An person who patterns the cryptanalysis.

Crypt analysis: The art of analizing cryptanalytic algorithms for placing the failings.

Plain Text: The information in its original signifier, besides called as clear text.

Cipher Text: The information after the encoding or the information which is unknown to us is called cipher text.

Encoding: The procedure of altering the field text into cypher text.

Decoding: The procedure of altering the cypher text into apparent text.

Encoding Algorithm: An algorithm defines how the information is transformed when original field text informations scrambled to code text. Both the information transmitter and receiver must knoe the algorithm used for informations transmittal. The receiver should utilize the same algorithm to decode the cypher ext back into original field text.

Encoding Key: Akey is a secret value, which is used as an input to the algorithm along with the field text informations when field text is converted to code text. The same secret key should be used to decode the cypher text back into field text.

BASICS OF SYMMETRIC ALGORITHMS:

Symmetric algorithms works utilizing a secret key, it means that whenever you want to code or decode the messages or informations utilizing symmetric algorithms. you need to supply this secret key which will be use ful to code or decode the data.following are the features of symmetric algorithms.

The strength of the encoding depends chiefly on the secured key.if you give the larger cardinal it harder to chop that code.since it will take more clip to the hackers to happen the key.

It is based on a simple mathematical operation. So it works faster, hence it is the best pick if you are working with the big sum of informations.

One drawback of this type of algorithms is that the secret key should be known to both parties ( that who is coding and who needs the information or information to decode. )

Symmetric based encoding can be broken by the hackers utilizing beastly force, but if you make a long key so it will take a long clip or even impossible to chop.

Since the secret key is user defined.so hackers can decode/decrypt your information utilizing beast force.but the larger key can protect your informations for long clip from checking.

SYMMETRIC ALGORITHM AND SYMMETRIC ALGORITHM CLASS:

The followers are the symmetric algorithm and its categories with some information of key

DES – the valid key size and default cardinal size is 64 spot and the default execution category is DESCryptoServiceProvider.

TRIPLE DES – the valid key size is 128,192 spot, defalt cardinal size is 128 spot and default execution category is TripleDESCryptoServiceProvider.

AES ( RijnDael ) – the valid key size is 128,192,256 spot, default cardinal size is 256and default execution category is RijnDaelManaged.

It should be noted here that all these algorithm categories are derived from abstract category symmetricAlgorithm. And you can see that each category supports different key sizes and these besides support for different IV sizes. As all these categories are abstract so we can non straight create any instace of any of these classes.But a SymmetricAlgorithm category expose a shared method named create which can be used to make concrete case of the category without worrying about how it is implemented.

TYPES OF CRYPTOGRAPHY:

There are 2 types of encoding techniques,

Symmetric or Conventional Encryption

Asymmetric or Public key Encyption

Symmetric or Conventional encoding is one of the old encoding strategies used in really early yearss and besides known as Secret cardinal Encryption. in this strategy both the transmitter and receiving system portions the same secret key for both encoding and decoding. This strategy uses old permutations and substitutions maps of mathematics to replace one character of apparent text with other to make encoding and decoding that is why its given the name as Symmetric Encryption strategy.

The undermentioned figure shown symmetric encoding strategy,

Sample screenshot

The algorithm used for symmetric cardinal encoding is called secret key algorithm.since secret key algorithms are chiefly used for coding the content of the message.so these besides called as content encoding algorithms.

The major exposure of secret cardinal encoding algorithm are need for sharing thesecret key.one manner of work outing this is by deducing the same secret key from the both terminals from a user given text twine ( Password ) and the algorithm used for this is called watchword based encoding algorithm.the another solution is to direct the key firmly from one terminal to other end.This is done utilizing another category of encoding called asymmetric encoding algorithm.

Strength of the symmetric cardinal encoding depends on the size of the used.for the same algorithm coding utilizing longer cardinal makes tougher to interrupt the algorithm than one done with the smaller key.strength of the key is non additive with the length of the key but doubles with each extra spot.

Following are the some symmetric cardinal algorithms used,

DES ( Data Encryption Standard ) – 64 Bit

TRIPLE DES ( Triple- Data Encryption Standard ) – 128 Bit

AES ( Advanced Encryption Standard ) – 256 Bit

ASYMMETRIC KEY ENCRYPTION:

A cryptanalytic system that uses two keys a populace key which is known to everyone and a private key known to merely the reciepent of the message is called asymmetric cryptanalysis, and the encoding of the message utilizing those public key and private key is known as asymmetric encoding.

A private key is chiefly used for coding the message-digest, in such an application the private key algorithm is called message -digest encoding algorithm.a public key is typically used for coding the secret key, such application private cardinal algorithm is calley cardinal encoding algorithm.

The undermentioned figure shows asymmetric encoding,

Asymmetrical encoding uses different keys for encoding and decoding. the decoding key is really difficult to deduce from the encoding key. The encoding key is public so that any one can code the message, nevertheless the decoding key is private so merely the receiving system is able to decode the message.it is common to put up cardinal braces within a web so that each user has a public and private key. The public key is made available to everyone so that anyone can code the messages but the private key is made available to the individual whom it belongs to.

Some asymmetric algorithms plants in opposite manner such as RSA algorithm.it allows procedure to work opposite way as well.a message can be encrypted with a private key and decrypted with a corresponding public key.if the receiver want to decode a message with Bob ‘s public key he must cognize that the message has come from Bob because no 1 else has transmitters private key.

The asymmetric algorithms used are

RSA ( Rivest, Shamir and Adleman )

Diffie – Hellman

VULNERABILITIES OF ENCRYPTION:

Interrupting symmetric encoding:

There are two methods of interrupting symmetric encoding

Brute force

Cryptanalysis

Brute force onslaught is a signifier of onslaught in which each possibility is tried until success isobtained.nothing but a cypher text is deciphered under different keys until the field text is recovered.no encrypted package that is safe from the Brute force method. But if the no possible keys is high enough it can do a plan astronomically hard to check utilizing Brute force. But the more spots in a cardinal the more secure it is.

Cryptanalysis is a signifier of onslaught that attacks the features of the algorithm to acquire a specific field text or the key used.

Weak Passwords:

In every sort of encoding package there is some sort of watchword that must be created so that the receivers of the information can read it.creating a strong watchword that can non be a easy guessed.so it is of import as taking the good algorithm and strong encoding package.

Remembering watchwords:

If you forget your watchword, you will non be able to decode informations that you have encrypted.be certain to do a backup transcript of your watchword and shop it in a safe topographic point.

Secret keys Exchanging and Storing:

Symmetric algorithms requires sharing a secret key, both the transmitter and receiving system needs the same key to code or decode data.anyone who knows the secret key can decode the message.so it is indispensable that the transmitter and receiving system have a manner to interchange secret keys in a sacure manner.the failing of symmetric algorithms is that if the secret key is discovered all messages can be decrypted.so secret key demand to be changed in a regular footing and maintain secure during distribution and while utilizing it.

BLOCK CIPHER:

Block cyphers operates in a strictly combinable manner with a fixed transmutation applied to a big block of field text on block by block basis.the most common block size is 8 bytes.each block is to a great extent processed, block cyphers provide a higher degree of security.however block cypher algorithms tends to put to death really easy.

Block cyphers uses the same encoding algorithm for each block, because of this ablock of field text will ever return the same cypher text when encrypted with the same key and the algorithm.because this behavior can be used to check a cypher, cipher manners are introduced that will modify the encoding procedure based on feedback from earlier block encodings. the resulting encoding provides higher degree of security than a simple block encoding.

BLOCK CIPHER MODES:

Cipher block altering manner ( CBC ) introduces feedback.before each block is encrypted, it is combined with the cypher text of the old block by a bitwise sole OR operation.this ensures that even if the field text contains many indistinguishable blocks, they will each encrypt to a different cypher text block.the low-level formatting vector is combined with the first field text block by a bitwise sole OR operation before the block is encrypted.

The cypher feedback manner ( CFB ) processes little increases of field text into cypher text,

Alternatively of treating an full block at a time.this manner uses a displacement registry that is one block in length and devided into subdivisions, for illustration, if the block size is 8 bytes, with one byte processed at a clip, the displacement registry is devided into 8 subdivisions.

The Electronic codification book ( ECB ) manner encrypts each block separately. This means that any blocks of field text that are indistinguishable and are in the same message, or in different message with same key, will be transformed into indistinguishable cypher text blocks.

Padding:

Most of the field text messages do non consists of figure of bytes that wholly filled blocks, frequently there are non plenty bytes to make full the last block.when this happens a embroidering twine will be added to the text.for illustration, if the block length is 64 spots and the last block contains merely 40 bits,24 spots of embroidering are added.

Padding Manner:

The PKCS # 7 embroidering threading consists of sequence of bytes each of which is equal to the entire figure of embroidering bytes added. For illustration, if 24 spots ( 3 bytes ) of embroidering demand to be added

The cushioning twine is “ 03 03 03 ” .

The Zeros embroidering threading consists of bytes set to zero.

STRENGTH OF THE CRYPTO SYSTEM

The strength of the cryto system depends chiefly on

Strength of an encoding algorithm

Secrecy of the key

Length of the key

Initialization vector

These all should work together within a cryptosystem when discoursing about strength of encryption.it refers to how difficult it is to calculate out the algorithm or key, whichever is non made public.attempts interrupt the crypto system involves go throughing the cardinal figure of possible ways that can be used to decode a message.Breaking a crypto system is accomplished by a beastly force attack.which means seeking every possible cardinal value until acquiring the ensuing field text depending on the algorithm and length of the key this can be an easy undertaking or one that is near to impossible. If a key can be destroyed by Pentium processor in three hours so the cypher is non strong at all.

Data Encryption Standard ( DES ) :

The DES algorithm is used to protect the confidential message from public, which is fundamentally private cardinal encoding scheme.To encrypt a text file and to decode the encrypted signifier of a file for acquiring the orginal field text the most widely used Data Encryption Standard algorithm is used. It was adopted in 1977 by National Bureau of Standards. It was desighned by IBM based on their ain lucifier cypher and input from NSA.

In DES information is encrypted in 64 spot Blocks utilizing a 56- Bit key.The algorithm transforms the 64- spot series of stairss into 64 -bit end product cipher text.the same stairss with the same key, are used to change by reversal the encoding i.e for decryption.Here fundamentally we give 64-Bit key as input but really it takes 56- Bit as effectual key and the staying 8 Spots are used as a para bits. This 56 -Bit key is sufficiently dependable at the clip of execution of DES algorithm.It was able to defy Brute force onslaughts and recent work on differential crypt analysis seems to bespeak that DES algorithm has strong internal construction.

Design Space of DES:

To implement DES algorithm wed esign the general word picture of DES encoding algorithm which consists of initial substitution of the 64-bit field text and so goes through 16 unit of ammunitions, where each unit of ammunition consists substitution and permutation of the field text spot and the input cardinal spot. And at last goes through a reverse initial substitution to acquire the 64-Bit cypher text. Decryption works by basically running DES backwords, foremost goes through an initial substitution with the same cardinal coevals in the opposite order that is cardinal generated In the last unit of ammunition is used foremost and so goes through an concluding substitution to undo the initial substitution.

DES Encoding:

The 64-bit input is given to an initial substitution to acquire 64-bit consequence ( merely the input with the spots shuffled ) . The 64-bit key is passed through an substitution map to acquire the 56-bit key which is used to bring forth 16 48-bit per unit of ammunition keys.by taking a different 48-bit subset fof the 56-bit each for the keys.Each unit of ammunition takes as input the 64-bit end product of the old unit of ammunition and the 48-bit per unit of ammunition key and produces a 64-bit end product. After the 16 round the 64-bit end product has its halves swapped and is so subjected to another substitution which happens to be the opposite of the initial substitution.

Detailss of Single Round:

The left and right rich persons of each 64-bit intermediate value are treated as separate 32 -bit measures labled as left ( L ) and right ( R ) .the overall processing expression at each unit of ammunition is as follows. Li= Ri-1, Ri= Li-1 XOR F ( Ri-1, Ki ) . the unit of ammunition cardinal Ki is 48-bits, the R input is 32-bits, this R input is foremost expanded to 48-bits utilizing substitution plus an enlargement tabular array. The resulting 48-bits are XORed with Ki.this 48-bit consequence base on ballss through a permutation map that produces a 32-bit end product in each halves to acquire 64-bit end product. The permutation consists of a set of 8 S-boxes in the mutilator map F. each of which accepts 6-bits as input and produces 4 -bits as end product.

Cardinal GENERATION:

The spots of the 64 spot input key are numbered from 1 to 64 and every 8th spot is ignored. The key is foremost subjected to substitution pick one, the ensuing 56-bit key is so treated as two 28-bit measures labled C0 and D0.

At each unit of ammunition C0-1 and D0-1 are individually subjected to a round left displacement or rotary motion of 1 or 2 spots that serve as input to following unit of ammunition and besides permuted pick two, which provides a 48 spot end product that serves buttocks input to the mutilator map F ( Ri-1, Ki ) .

DES DECRYPTION:

The decoding procedure works basically by running the DES backwards.to decrypt a block we should foremost run it through the initial substitution to undo the concluding permutation.we do the the same cardinal coevals, though we use the keys in opposite order ( first we use K16, the key generated at last ) . Then we run 16 unit of ammunitions merely like for encoding. after 16 unit of ammunitions of decoding the end product has its halves swapped and is so subjected to the concluding substitution.

AES ALGORITHM IMPLEMENTATION:

AES stands for Advanced Encryption Standard, and it is a symmetric cardinal encoding technique which replaces the normally used DES Data Encryption Standard.

It was the consequence of a worldwide call for entries of encoding algorithms issued by the US Government ‘s National Institute of Standards and Technology ( NIST ) in 1997 and completed in 2000.The winning algorithm Rijndael are developed by two Belgian cryptanalysts Vincent Rijmen and Joan Daemen. AES provides strong encoding and was selected by NIST as a Federal Information Processing Standard in November 2001 ( FIPS-197 ) .

The AES algorithm uses three key sizes 128- , 192- 256-bit encoding key. Each encoding cardinal size causes algorithm to move in a different mode. So the increasing key sizes non merely offer a big figure of spots with which you can scramble the information, but besides increases the complexness of the cypher algorithm.

ENCRYPTION ALGORITHM SELECTION:

The Advanced Encryption Algorithm ( AES ) was selected for several grounds. The encoding nucleus will necessitate to back up a broad scope of applications for coding a big sum of informations.

Two standard algorithms are compared the Advanced Encryption Standard ( AES ) and the Data Encryption Standard ( DES ) .both of these are symmetric algorithms. The DES algorithm supports a cardinal length of 56- spots where as the AES algorithm supports cardinal lengths of 128, 192, 256- Bits. Given that the block of encrypted informations and a block of decrypted information is known, if the 56 -bit DES algorithm could be broken in 1 2nd merely by seeking every possible key the same method utilizing the 128 -bit AES algorithm will take about 1.5* 10^14 old ages to break.192 -bit AES algorithm, 2.8* 10^33 old ages, the 256-bit AES algorithm 5.1* 10^52 old ages. It is easy to see that an algorithm with more cardinal spots has a much greater impact on the security.

DESIGN SPACE OF AES:

The AES algorithm is based on simple mathematical transmutations whose opposites are hard to calculate without the key. The algorithm has 4 basic transmutations