Rc4 blowfish idea
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RC4 is a stream cipher designed in 1987 by Ron Rivets for RSA Security. It uses random permutation to generate a keystream from an initialization vector and variable-length key. The algorithm initializes a state vector S by permuting its entries based on a temporary vector T derived from the key. It then cycles through S, swapping entries to generate a keystream byte. Blowfish is a symmetric block cipher developed by Bruce Schneier in 1993. It is designed to be fast, compact, simple and have a variable key length up to 448 bits. The key is used to generate 18 subkeys and four S-boxes used in its Feistel network structure. IDEA is an
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RC4 Algorithm :
RC4 is a Stream cipher designed in 1987 by Ron Rivets for RSA Security.
It is variable key –size stream cipher with byte-oriented operations.
The algorithm is based on the use of random permutation.
o K- is Key
o S- S is State vector having plain text.
INITIALIZATION OF S :
To begin,the entriesof Sare setequal tothe valuesfrom0 through255 in ascendingorder;that
is, S[0] 0, S[1] 1, . . ., S[255] 255.
A temporary vector,T, is also created.
If the length of the key K is 256 bytes, then K is transferred to T. Otherwise, for a key of length
keylenbytes,the firstkeylenelements of T are copied from K, and then K is repeated as many times as
necessary to fill out T.These preliminary operations can be summarized as:
Figure 1 Initialization of S
Initial Permutation of S:
Nextwe use T to produce the initial permutationof S.Thisinvolvesstarting with S[0] and going through
to S[255] and, foreach S[i],swappingS[i]with another byte in S according to a scheme dictated by T[i]:
STREAM GENERATION: Once the S vector is initialized, the input key is no longer used. Stream
generationinvolvescyclingthroughall the elementsof S[i] and,foreachS[i],swappingS[i] with another
byte in S according to a scheme dictated by the current configuration of S. After S[255] is reached, the
process continues, starting over again at S[0]:](https://image.slidesharecdn.com/xmomrh9btdggoupwqme1-signature-c786feda5808b774b627e3bb07175e585f552ad7d42ac5dcf7b3713dc7667c76-poli-170317063705/85/Rc4-blowfish-idea-1-320.jpg)
Rc4 blowfish idea
- 1. 1 RC4 Algorithm : RC4 is a Stream cipher designed in 1987 by Ron Rivets for RSA Security. It is variable key –size stream cipher with byte-oriented operations. The algorithm is based on the use of random permutation. o K- is Key o S- S is State vector having plain text. INITIALIZATION OF S : To begin,the entriesof Sare setequal tothe valuesfrom0 through255 in ascendingorder;that is, S[0] 0, S[1] 1, . . ., S[255] 255. A temporary vector,T, is also created. If the length of the key K is 256 bytes, then K is transferred to T. Otherwise, for a key of length keylenbytes,the firstkeylenelements of T are copied from K, and then K is repeated as many times as necessary to fill out T.These preliminary operations can be summarized as: Figure 1 Initialization of S Initial Permutation of S: Nextwe use T to produce the initial permutationof S.Thisinvolvesstarting with S[0] and going through to S[255] and, foreach S[i],swappingS[i]with another byte in S according to a scheme dictated by T[i]: STREAM GENERATION: Once the S vector is initialized, the input key is no longer used. Stream generationinvolvescyclingthroughall the elementsof S[i] and,foreachS[i],swappingS[i] with another byte in S according to a scheme dictated by the current configuration of S. After S[255] is reached, the process continues, starting over again at S[0]:
- 2. 2 BLOWFISH: BLOWFISH isa symmetricblockcipherdevelopedbyBruce Schneier.BLOWFISH wasdesignedtohave the followingcharacteristics: Fast: Blowfishencryptsdataon 32 bit microprocessorsata rate of 18 clock cyclesperbyte. Compact:Blowfishcanrun inlessthan5K of memory. Simple:Blowfish’ssimple structure iseasytoimplementandeasesthe taskof determiningthe strength of the algorithm.
- 3. 3 Variable secure:The keylengthisvariable andcanbe as longas 448 bits.Thisallowsa tradeoff between higherspeedandhighersecurity. Subkeyand S-Box Generation: Blowfishmakesuse of akeythat rangesfrom32 bitsto 448 bits( 1 to 14 32 bitwords). Keyisusedto generate 18 sub keyseachof 32 bitsandfour 8*32 S-boxes. The keysare storedinK-array:
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- 5. 5 IDEA (INTERNATIONAL DATA ENCRYPTION ALGORITHM):
- 6. 6 Keygenerationanduse of subkeys: The processcontinuesforrestof the rounds.(Look additional informationforbetterclarification) OperationsusedinEverysingle round: 1. Multiplication 2. Addition 3.Bitwise XOROperator
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- 8. 8 ADDITIONAL INFORMATIONFOR BETTER UNDAERSTANDING OF ALGORITHM What happensin each single round:
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