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Topic: Simple XOR cipher

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Vigenere cipher

Caesar cipher

Vernam cipher

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	Simple XOR cipher - Wikipedia, the free encyclopedia
		In cryptography, a simple XOR cipher is a relatively simple encryption algorithm that operates according to the principles:
		Its primary merit is that it is simple to implement, and that the XOR operation is computationally inexpensive.
		Also, the XOR cipher is completely vulnerable to the known-plaintext attack, since (plaintext) XOR (ciphertext) = (key).
	en.wikipedia.org /wiki/Simple_XOR_Cipher (257 words)

	What is XOR encryption?
		XOR encryption is a trivially simple symmetric cipher which is used in many applications where security is not a defined requirement.
		The XOR operator is used to "flip" bits (zeroes and ones) in a piece of plaintext to create a ciphertext.
		Understanding XOR and the other binary operators is a necessary step on the path to becoming a cryptologist.
	www.tech-faq.com /xor-encryption.shtml (275 words)

	CPSC 467a Lecture Notes 4
		A stream cipher has two components, the cipher that is used to encrypt a given character, and a keystream generator that produces a different key to be used for each successive letter.
		For the simple XOR cipher to be secure, a cryptographically strong pseudorandom number generator must be used.
		With a stream cipher, security rests with the keystream generator, for the ciphers used to encrypt the individual characters are all subject to known-plaintext attacks.
	zoo.cs.yale.edu /classes/cs467/2005f/attach/ln04.html (1025 words)

	Ritter's Cipher Boutique
		Block ciphers process each message in blocks or "chunks," but even if only one byte of a block is needed, the entire block must be ciphered and transported.
		Normally, the keyspace of this sort of cipher is limited by the size of the RNG used to key the substitutions, and it is easy to have a true keyspace of thousands of bits.
		Normally, the keyspace of this sort of cipher is limited by the size of the RNG used to key the tables or squares, and it is easy to have an efficient true keyspace of many thousands of bits.
	www.ciphersbyritter.com /CIPHBOU.HTM (2848 words)

	The Colossus - Tony Sale
		The various components of Colossus were the optical reader system, the master control panel, the thyratron rings and their driver circuits, the optical data staticisors and delta calculators, the shift registers, the logic gates, the counters and their control circuits, the span counters, the relay buffer store and printer logic.
		First the delta outputs from channel 5 of the paper tape reader is combined in an XOR gate with the delta output of the K5 thyratron ring.
		Then this result is XORed with the XOR output of delta channel 4 and the delta output of the K4 thyratron ring.
	www.codesandciphers.org.uk /virtualbp/fish/colossus.htm (2322 words)

	FIRST ADVANCED ENCRYPTION STANDARD (AES) CANDIDATE CONFERENCE
		This permutation uses addition modulo 2^64 and the XOR operation with two fixed constants and another constant that is chosen from a table according to six of the data bits.
		MARS is a cipher with thirty-two modified Feistel rounds structured as follows: key addition, eight rounds of "unkeyed forward mixing," eight rounds of "keyed forward transformation," eight rounds of "keyed backwards transformation," eight rounds of "unkeyed backwards mixing," and key subtraction.
		The presenter, Joan Daemen, explained the elements of the cipher: for example, he cited the diffusion properties of the linear layer, and he claimed that the s-box would be difficult to model algebraically.
	www.ieee-security.org /Cipher/ConfReports/conf-rep-aes.html (5942 words)

	Software Project SkyNavigator
		Cipher is a very simple but fast encryption program to secure especially huge amount of data.
		For the reason that Cipher simply uses an XOR operation to generate the encrypted file out of the original file and the pseudo random sequence, it is not recommended to use the same pass phrase for two different files you want to encode.
		For the reason that the program uses an XOR operation for encryption the decryption of a file works exactly in the same way as the encryption.
	home.wtal.de /shotto/cipher.htm (441 words)

	Cryptography Tutorials - Herong's Tutorial Notes - Cipher - DES Algorithm
		Block Cipher - An encryption scheme that "the clear text is broken up into blocks of fixed length, and encrypted one block at a time".
		Usually, a block cipher encrypts a block of clear text into a block of cipher text of the same length.
		In this case, a block cipher can be viewed as a simple substitute cipher with character size equal to the block size.
	www.herongyang.com /crypto/cipher_des.html (316 words)

	Improved Caesar-like ciphers
		This cipher is called a polyalphabetic substitution cipher, because several different substitutions are made depending on the position of the character within the text.
		This cipher takes its name after Blaise de Vignère, although it is actually a corruption of the one he introduced in 1585.
		In fact, as late as 1917, this cipher was described as ``impossible of translation'' in a respected journal (Scientific American), even though the means to break it had been well known among cryptographers for at least 50 years.
	www.math.sunysb.edu /~scott/Book331/Improved_Caesar_like_cipher.html (2417 words)

	Blowfish Paper
		Almost all block ciphers since Lucifer [5,21] are Feistel ciphers, and all have a flat keyspace (with the possible exception of a few weak keys).
		XOR P1 with the first 32 bits of the key, XOR P2 with the second 32-bits of the key, and so on for all bits of the key (possibly up to P14).
		The XOR can also be considered to be part of the non-reversible function, Ni, occurring at the end of the function.
	www.schneier.com /paper-blowfish-fse.html (4085 words)

	nCipher - Glossary
		A special class of iterated block ciphers where the ciphertext is calculated from the plaintext by repeated application of the same transformation called a round function.
		A secret key cipher in which the key is a truly random sequence of bits that is as long as the message itself, and encryption is performed by XORing the message with the key.
		A property of a stream cipher, stating that the keystream is generated independently of the plaintext and ciphertext.
	www.ncipher.com /company/investor_relations/glossary.php (4722 words)

	Jail Cell RC4
		I realize that others have tried to construct secure paper-and-pencil ciphers, but I would be very appreciative of any input you may have.
		Because RC4 is a stream cipher and the same S-box configuration cannot be used to send more than one message, K needs to be modified for each message.
		Since the cipher relies on human computation, there is likely to be a non-negligible rate of introduction of errors into the cipher.
	www.mindflare.com /cipher (2173 words)

	PMC Ciphers, Inc. - Partners and Affiliates (Site not responding. Last check: 2007-11-04)
		Simple xor instructions, as well as addition and subtraction are cryptographically weak, but the general code assembly method can be demonstrated best with these.
		If the cipher block size is small (under 64 bytes), and if the ciphering key is not changed frequently, it may be possible to build a codebook of block values with their intended meanings.
		Through extensive ciphering of fixed plaintext data under a variety of different keys, it may sometimes be possible to associate key bits with the statistical value of some ciphertext bits.
	www.pmc-ciphers.com /technology/polymorphic_cipher.php (3374 words)

	project4 (Site not responding. Last check: 2007-11-04)
		The choice of which cipher to use is left up to you.
		(XOR data with a key to encrypt, then XOR it again with the same key to decrypt.) Alternatively, you may want to implement a more secure algorithm, such as DES, Blowfish, or even RSA.
		Your encryption and decryption routine should be written in assembly for speed, and your main program should be written in C for portability.
	www.cs.usfca.edu /~afedosov/cs210/project4.html (446 words)

	Ciphers By Ritter: Cryptography and Technology
		The cipher is keyed by constructing a particular orthogonal Latin square pair for each mixing element, which is fairly easy to do.
		A block cipher based on transposition, using stream cipher techniques, generates a perfect secrecy transformation on a block-by-block basis.
		A 4-bit cipher model which uses keyed 2-bit tables is presented as a challenge to explore the strength of the structure.
	www.ciphersbyritter.com (5134 words)

	Software security for developers: One-time pads
		In practice, commonly used ciphers that are believed to be secure may or may not actually be secure.
		With symmetric key ciphers, the "best case" is more often than not related to the size of the key space -- unless there's known to be a better attack than trying every possible key until the data is unveiled (the brute force attack).
		Starting on the first page of the pad, the first letter of the cipher text was converted to a number, and subtracted from the number on the pad.
	www-106.ibm.com /developerworks/library/s-pads.html (3240 words)

	Is Integrity-Aware Encryption Difficult?
		The result of this XOR is used to select bits from the most significant block length's worth of bits from the second and third counters, where a 0 bit selects the corresponding bit from the second counter, and a 1 bit selects the corresponding bit from the third counter.
		No provision for a checksum is made; it is presumed that a simple XOR of the blocks in a message, encrypted as the last block, would serve as a checksum if the encryption mode were truly as perfect as intended.
		If one uses XOR instead of taking the difference between the two outputs, for order 8, the best score shrinks to 4 from 6, and it appears that even for a random S-box instead of one designed to maximize the score, subtraction is better for this purpose.
	www.quadibloc.com /crypto/co040604.htm (6799 words)

	EllisLab.com :: Data Encryption Using XOR (Site not responding. Last check: 2007-11-04)
		The XOR operator turns a bit on if only one of its operands is on, but not both.
		Data Encryption Using XOR By Rick Ellis, at EllisLab.com http://www.ellislab.com/data_encryption_using_xorThe term “operator” usually refers to a common math operator, like add, subtract, divide, etc. In programming, however, there are other types of operators, such as Bitwise operators, that let you manipulate bits.
		It's fairly simple, but it shows what can be done if you're willing to roll up your sleeves and do some custom queries and scripting.
	www.ellislab.com /data_encryption_using_xor (1796 words)

	Cryptanalysis of CipherSaber-1
		CipherSaber 1 is a way of using Ron Rivest's RC4 cipher as a practical symmetric key cryptosystem.
		In a stream cipher it is essential that the same key never be used twice.
		It might be better for each user to determine the largest value of N that is tollerable on their computer and to agree to use the smaller of the two acceptable N values when communicating with another CipherSaber user.
	www.ciphersaber.gurus.com /cryptanalysis.html (2552 words)

	What are substitution and transposition ciphers?
		An even more complex substitution cipher can be made by having each character of the alphabet correspond to a different letter of the alphabet, without a set pattern.
		The Vernam Cipher, or one time pad, is a simple substitution cipher where the key length equals the message length.
		ROT-13 is a simple substitution cipher used to encode messages on Usenet.
	www.tech-faq.com /substitution-transposition-cipher.shtml (275 words)

	Stream Ciphers
		The same simple mathematical properties that make them vulnerable to cryptanalysis at least ensure that they will generate sequences with a long period.
		Although one usually thinks of pseudo-random number or bit generation when one thinks of stream ciphers, the cipher produced by a rotor machine, which is a changing substitution (as opposed to a changing displacement, as produced by a Hagelin lug and pin machine) is still classed as a stream cipher.
		The Cipher Feedback (CFB) mode of DES is an example of this class of cipher, although in that case one would need to know the boundary between 8-byte blocks to recover.
	www.quadibloc.com /crypto/co0408.htm (302 words)

	What's up with WEP? (Site not responding. Last check: 2007-11-04)
		The cipher text results from applying the XOR function to the plain text and the keystream.
		The authors noted that stream ciphers (like RC4) are vulnerable if two messages are encrypted with the same IV and secret key.
		If the cipher texts are XORed together, the keystream will cancel out and the XOR of the two plain texts will remain.
	www-106.ibm.com /developerworks/library/s-wep/?article=wir (2033 words)

	Why Are One-Time Pads Perfectly Secure? (Site not responding. Last check: 2007-11-04)
		As with all symmetric ciphers, the sender must transmit the key to the recipient via some secure and tamperproof channel, otherwise the recipient won't be able to decrypt the ciphertext.
		The key for a one-time pad cipher is a string of random bits, usually generated by a cryptographically strong pseudo-random number generator (CSPRNG).
		It's that simple, and it's perfectly secure, as long as the key is random and is not compromised.
	world.std.com /~franl/crypto/one-time-pad.html (494 words)

	ASPN : Python Cookbook : Simple XOR keyword Encryption (Site not responding. Last check: 2007-11-04)
		You probably don't want to use this -- encryption with XOR is notoriously weak and methods for ciphertext-only cryptanalysis have been around for centuries: do a Google for "Vigenere", a similar scheme based on the 26-letter alphabet.
		If you really need a simple cipher, consider implementing something like RC5 or TEA/XTEA which can be described in just a few lines of code.
		XOR encryption is what is used in the "perfect" encryption scheme of the one-time-pad.
	aspn.activestate.com /ASPN/Cookbook/Python/Recipe/266586 (496 words)

	In a word: Moof. - Not-so-simple Substitution Cipher
		He had been given a few files full of hex bytes (in ASCII,) encrypted with a simple mono-alphabetic substitution cipher.
		Typically a substitution cipher is something to be laughed at when it comes to security, but there was a slight twist on this one.
		The normal way to attack a substitution cipher is to create a frequency distribution of the cipher text and the "probable plaintext", and correlate the results.
	blog.case.edu /moof/2005/07/20/notsosimple_substitution_cipher (486 words)

	Random Neuron Firings
		Its fairly easy for a person to figure out a simple XOR or base64 encoding method, which are probably the most common "lazy" encryption methods.
		Encrypting data with a fairly secure method is extremely simple.
		I put together a really simple utility that provides 3DES encryption of a String, and returns a base64 representation of the cipher text, and will decrypt that same cipher.
	www.savoirtech.com /roller/page/jgenender?entry=cipher_text_for_storage (657 words)

	A KEY EXCHANGE PROTOCOL
		If the cipher is commutative, this results in B(K), which she sends back to Bob, who can decrypt it with -B. The need for a commutative cipher is explained by the fact that the decryption is done in the SAME order as the encryption instead of REVERSE order.
		A commutative cipher is one in which the order of encryption and decryption is interchangeable, just as the order of multiplication is interchangeable; i.e., ABC=ACB=CBA. A simple XOR with a the individual keys is such a commutative cipher.
		The attack that makes this protocol less than optionally secure when XOR is the cipher requires the attacker to capture all three messages, and to know the algorithm that is being used to encrypt; not too difficult a task for NSA, for example, and quite possibly others.
	www.afn.org /~afn21533/keyexchg.htm (1481 words)

	Cycom AB - Reverse Remote Shell
		With a symmetric cipher both the listener and the connector has to use the same pass phrase in order to communicate.
		This cipher is quite weak and should not be considered decent encryption.
		Since this XOR cipher loops the key for the data received/transmitted, the engine will be initialized with a 144 byte ascii hash (SHA1+MD5+SHA1+MD5).
	www.cycom.se /dl/rrs (1628 words)

	DevPrime - Articles - Anatomy of a Symmetric Cipher (Site not responding. Last check: 2007-11-04)
		The ciphers in use that are industry standards have survived years (sometimes decades) of abusive attempts to crack them by means most programmers would never think of.
		The cipher implementation class has the actual code for the implementation of the cipher and we'll stick to the established naming convention for this class.
		If we are in stream cipher mode, we will encrypt the keystream register, XOR the appropriate byte with the next plain text byte, set that as the output, and shift the keystream register appropriately.
	devprime.com /Article2017.aspx (7506 words)

	Plug-In Encryption Solution?
		It is a variable key-size stream cipher with byte-oriented operations.
		Analysis shows that the period of the cipher is overwhelmingly likely to be greater than 10^100.
		Eight to sixteen machine operations are required per output byte, and the cipher can be expected to run very quickly in software.
	www.blitzbasic.com /Community/posts.php?topic=54854 (441 words)

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