Caesar Nix

Cryptography

Jason Andress , in The Nuts of Data Security (Second Edition), 2014

Caesar nada

The Caesar cipher is a classic case of aboriginal cryptography and is said to take been used by Julius Caesar. The Caesar cipher is based on transposition and involves shifting each letter of the plaintext bulletin by a sure number of messages, historically three, as shown in Figure 5.1. The ciphertext tin can be decrypted by applying the same number of shifts in the opposite direction. This type of encryption is known as a commutation cipher, due to the substitution of one letter for some other in a consistent fashion.

Figure v.1. Caesar nada.

A more recent variation of the Caesar cipher can be found in the ROT13 cipher. ROT13 uses the same mechanism as the Caesar cipher merely moves each letter xiii places frontwards. The convenience of moving xiii places lies in the fact that applying some other round of encryption with ROT13 also functions as decryption, every bit two rotations volition return us to the original starting place in the alphabet. Utilities for performing ROT13 tin be found in the basic set of tools that ship with many Linux and UNIX operating systems. There are a number of uncomplicated systems that are congenital around simple transposition.

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Domain 3: Security Engineering (Technology and Management of Security)

Eric Conrad , ... Joshua Feldman , in CISSP Study Guide (Third Edition), 2016

Caesar Nix and other Rotation Ciphers

The Caesar Nada is a monoalphabetic rotation cipher used by Gaius Julius Caesar. Caesar rotated each letter of the alphabet of the plaintext forwards three times to encrypt, and so that A became D, B became E, etc., as shown in Table 4.6.

Tabular array 4.half-dozen. Caesar (Rot-iii) Cipher

Table 4.7 shows how "Set on AT DAWN" encrypts to "DWWDFN DW GDZQ" using the Caesar Cipher. Annotation that rotating iii letters is capricious; any number of messages (other than 26, assuming an English alphabet) may be rotated for the same event.

Table 4.7. Encrypting "ATTACK AT DAWN" with the Caesar Cipher

Some other mutual rotation aught is Rot-13, often used to conceal information on message board systems such as Usenet. For example, details that could "spoil" a film for someone who had not seen it would exist encoded in Rot-thirteen: "Qrpxneq vf n ercyvpnag!" Many Usenet readers had a Rot-xiii function to quickly decode whatsoever such messages.

Rot-13 rotates 13 characters, so that "A" becomes "N," "B" becomes "O," etc. A dainty feature of Rot-13 is one application encrypts (albeit weakly); a second application decrypts (the equivalent of Rot-26, where "A" becomes "A" once more).

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A Cryptography Primer

Scott R. Ellis , in Computer and Information Security Handbook, 2009

The Shift Naught

Also known as the Caesar zippo, the shift cipher is one that anyone tin readily sympathize and remember for decoding. It is a form of the commutation zilch. By shifting the alphabet a few positions in either direction, a elementary sentence can become unreadable to casual inspection. Example 2.ane is an case of such a shift.

Example two.1

A sample cryptogram. Try this out:

Gv Vw, Dtwvg?

Hint: Caesar said it, and it is Latin. ii

Interestingly, for cryptogram word games, the spaces are e'er included. Frequently puzzles use numbers instead of letters for the commutation. Removing the spaces in this particular example can make the ciphertext somewhat more than secure. The possibility for multiple solutions becomes an issue; whatever number of words might fit the pattern.

Today many software tools are available to apace and hands decode most cryptograms (at to the lowest degree, those that are not written in a dead linguistic communication). Y'all can accept some fun with these tools; for example, the name Scott Ellis, when decrypted, turns into Yet Books. The name of a friend of the author'southward decrypts to "His Sinless." It is apparent, then, that smaller-sample elementary substitution ciphers can take more than ane solution.

Much has been written and much has been said almost frequency analysis; it is considered the "end-all and exist-all" with respect to cipher decryption. This is non to be confused with nix breaking, which is a modern attack against the actual cryptographic algorithms themselves. However, to think of simply plugging in some numbers generated from a Google search is a scrap naïve. The frequency chart in Tabular array 2.five is commonplace on the Web.

Tabular array 2.5. "In a random sampling of yard letters," this design emerges.

Letter Frequency
E 130
T 93
N 78
R 77
I 74
O 74
A 73
S 63
D 44
H 35
50 35
C xxx
F 28
P 27
U 27
M 25
Y 19
G 16
W sixteen
V 13
B nine
X five
K 3
Q 3
J two
Z 1
Total 1000

It is beyond the scope of this affiliate to delve into the accuracy of the table, just suffice it to say that our ain analysis of Affiliate nineteen's 118,000 characters, a technical text, yielded a much different result; see Table ii.6. Perhaps it is the significantly larger sample and the fact that information technology is a technical text that makes the results different after the top two. Additionally, where computers are concerned, an actual frequency assay would take into consideration all ASCII characters, every bit shown in Table 2.vi.

Table 2.6. Using MS Admission to perform some frequency analysis of Chapter 19 in this book. Characters with fewer repetitions than z were excluded from the return. Graphic symbol frequency analysis of different types of communications yield slightly different results.

Chapter 19 Letters Frequency
due east xiv,467
t x,945
a 9239
i 8385
o 7962
due south 7681
n 7342
r 6872
h 4882
fifty 4646
d 4104
c 4066
u 2941
m 2929
f 2759
p 2402
y 2155
g 1902
w 1881
b 1622
v 1391
. 1334
, 1110
thou 698
0 490
x 490
q 166
7 160
* 149
5 147
) 147
( 146
j 145
3 142
6 140
Æ 134
ò 134
ô 129
ö 129
4 119
z 116
Total 116,798

Frequency analysis is not difficult; one time all the messages of a text are pulled into a database program, it is fairly straightforward to do a count of all the indistinguishable values. The snippet of lawmaking in Instance two.2 demonstrates one way whereby text can be transformed into a single column and imported into a database.

Example 2.ii

 one: Sub Letters2column ()

 two: Dim bytText () As Byte

 3: Dim bytNew() As Byte

 4: Dim lngCount Equally Long

 v: With ActiveDocument.Content

 6: bytText = .Text

 7: ReDim bytNew((((UBound(bytText()) + ane) * 2) - 5))

 eight: For lngCount = 0 To (UBound(bytText()) - 2) Pace 2

 9: bytNew((lngCount * ii)) = bytText(lngCount)

ten: bytNew(((lngCount * ii) + ii)) = 13

11: Side by side lngCount

12: .Text = bytNew()

thirteen: Cease With

14: End Sub

The cryptograms that use formatting (every discussion becomes the same length) are considerably more difficult for basic online decryption programs to crack. They must have into consideration spacing and give-and-take lengths when because whether or not a string matches a word. It stands to reason, so, that the formulation of the cipher, where a exchange that is based partially on frequency similarities and with a whole lot of obfuscation so that when messages are decrypted they take ambiguous or multiple meanings, would be desirable for simple ciphers. Still, this would only be true for very short and very obscure messages that could be code words to decrypt other messages or could simply be sent to misdirect the opponent. The amount of ciphertext needed to successfully break a cipher is chosen unicity distance. Ciphers with small unicity distances are weaker than those with large ones.

Ultimately, substitution ciphers are vulnerable to either word-blueprint analysis, letter-frequency analysis, or some combination of both. Where numerical information is encrypted, tools such every bit Benford's Police can be used to elicit patterns of numbers that should be occurring. Forensic techniques contain such tools to uncover accounting fraud. And so, though this particular cipher is a kid's game, it is useful in that it is an underlying principle of cryptography and should be well understood earlier continuing. The primary purpose of discussing it hither is as an introduction to ciphers.

Further topics of interest and places to find information involving substitution ciphers are the chi-square statistic, Edgar Allan Poe, Sherlock Holmes, Benford's Constabulary, Google, and Wikipedia.

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Cryptography

In Hack Proofing Your Network (2d Edition), 2002

Summary

This chapter looked into the meaning of cryptography and some of its origins, including the Caesar Goose egg. More modern branches of cryptography are symmetric and disproportionate cryptography, which are also known as secret central and public key cryptography, respectively.

The most common symmetric algorithms in use today include DES, AES, and IDEA. Since DES is showing its historic period, we looked at how NIST managed the evolution of AES every bit a replacement, and how Rijndael was selected from five finalists to get the AES algorithm. From the European perspective, nosotros saw how Thought came to be developed in the early 1990s and examined its advantages over DES.

The early on evolution of disproportionate cryptography was begun in the mid-1970s by Diffie and Hellman, who adult the Diffie-Hellman primal commutation algorithm as a ways of securely exchanging data over a public network. After Diffie-Hellman, the RSA algorithm was developed, heralding a new era of public key cryptography systems such as PGP. Cardinal differences between public key and symmetric cryptography include public key cryptography'southward reliance on the factoring problem for extremely large integers.

Brute force is an effective method of breaking most forms of cryptography, provided you have the time to wait for keyspace exhaustion, which could have anywhere from several minutes to billions of years. Cracking passwords is the most widely used application of brute forcefulness; programs such every bit L0phtcrack and John the Ripper are used exclusively for this purpose.

Even secure algorithms can be implemented insecurely, or in ways not intended by the algorithm's developers. Homo-in-the-middle attacks could cripple the security of a Diffie-Hellman key exchange, and even DES-encrypted LANMAN countersign hashes can be broken quite hands. Using easily broken passwords or passphrases as clandestine keys in symmetric algorithms can have unpleasant furnishings, and improperly stored private and secret keys can negate the security provided past encryption altogether.

Data is sometimes concealed using weak or reversible algorithms. We saw in this chapter how weak ciphers are subject to frequency analysis attacks that employ linguistic communication characteristics to decipher the bulletin. Related attacks include relative length analysis and similar plaintext analysis. We saw how vendors sometimes conceal information using XOR and Base64 encoding and looked at some sample code for each of these types of reversible ciphers. We too saw how, on occasion, information is compressed as a ways of obscuring it.

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Cryptography

Eric Knipp , ... Edgar Danielyan Technical Editor , in Managing Cisco Network Security (Second Edition), 2002

Monoalphabetic Ciphers

A monoalphabetic cipher is any zippo in which each character of the alphabet is replaced past some other character in a 1-to-one ratio. Both the Caesar Cipher and ROT13, mentioned earlier in the chapter, are classic examples of monoalphabetic ciphers. Some monoalphabetic ciphers scramble the alphabet instead of shifting the messages, so that instead of having an alphabet of ABCDEFGHI- JKLMNOPQRSTUVWXYZ, the cipher alphabet order might be MLNKB-JVHCGXFZDSAPQOWIEURYT. The new scrambled alphabet is used to encipher the message such that G   =   A, L   =   B…T   =   Z. Using this method, the cleartext message "Surreptitious" becomes "OBNQBW."

Yous will rarely find these types of ciphers in use today outside of discussion games because they can be easily broken by an exhaustive search of possible alphabet combinations and they are likewise quite vulnerable to the language assay methods we described. Monoalphabetic ciphers are admittedly vulnerable to frequency analysis considering even though the messages are substituted, the ultimate frequency appearance of each letter will roughly represent to the known frequency characteristics of the language.

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Resistance Strategies

Timothy J. Shimeall , Jonathan M. Spring , in Introduction to Information Security, 2014

Substitution Ciphers

Substitution ciphers encrypt the plaintext by swapping each letter of the alphabet or symbol in the plaintext by a dissimilar symbol as directed by the key. Perhaps the simplest substitution cipher is the Caesar cipher, named after the human who used it. To modernistic readers, the Caesar zippo is peradventure amend known through the Captain Midnight Lawmaking-O-Graph and hush-hush decoder rings that even came inside Kix cereal boxes [four]. Technically speaking, the Caesar cipher may be differentiated from other, more than complex substitution ciphers by terming it either a shift cipher or a mono-alphabetic cipher; both are correct.

Allow's take a await at an instance. Since case does not matter for the zero, we tin apply the convention that plaintext is represented in lowercase letters, and ciphertext in uppercase. Spaces in the ciphertext are just added for readability; they would be removed in a existent awarding of the nada to brand attacking the ciphertext more difficult.

Plaintext: speak, friend, and enter

Key: E

Ciphertext: WTIEOD JVMIRHD ERH IRXIV

This cipher's method of combining the plaintext and the key is actually add-on. Each alphabetic character of the alphabet is assigned a number—that is, A is 0, B is one, and then on, through Z at 25. The set of letters used can be more than complex. This example also uses the comma character as the final grapheme of the alphabet, 26. The spaces in the plaintext are ignored, for now. For each letter in the plaintext, it is converted to its number, then the value for the key is added, and the resulting number is converted back to a alphabetic character: S is 18 and East is 4. So the issue is 22, or Westward. This is repeated for each grapheme in the plaintext. Decryption is simple—the inverse of addition is just subtraction, so the key is subtracted from the ciphertext to go the plaintext back. Of course, 22−four=18.

There are obviously lots of problems with this. To decrypt the message, one could chop-chop effort all 26 keys. The number of possible keys is called the central infinite. If the key space is minor enough that an adversary tin try all possible keys in a "short" amount of fourth dimension, and so it doesn't matter what the algorithm is, it is essentially useless. This is known as the sufficient key space principle [i, p. eleven]. "Short" is in quotes because the verbal length of time depends on the use of the key in the cryptosystem and the risk model that the defender has for how long the communication needs to be secret. Nonetheless, if the adversary tin can effort all of the keys in a day or a week, so the key infinite is generally likewise minor for general commercial use. On modernistic computer systems, well-nigh 280 keys can exist tried in a "short" amount of time, so any algorithm employed past the defender to resist assault should take a primal space at to the lowest degree this large. However, if the defender does not want to accept to change the cipher relatively before long, we suggest a rather larger central space, and so does NIST (National Institute of Standards and Technology) [5].

In this simple shift cipher, the central space is small. The best case for a mono-alphabetic cipher does non have a modest key space, however. If A is randomly assigned to one of the 26 letters, B 1 of the remaining 25, C to i of the remaining 24, and so on, we create a table for the primal that looks like this:

Plaintext character: a b c d e f g h i j k l m n o p q r s t u v due west x y z

Key character: X F Q G A Due west Z S E D C V B Northward M L K J H G T Y U I O P

This is chosen a mono-alphabetic substitution goose egg. For this cipher, there is no equivalent improver for encrypting the plaintext. The primal is the whole table, and each letter is substituted by the key character. Decryption uses the same key, but y'all expect upwardly the ciphertext grapheme on the lesser row and substitute the top-row character. The previous plaintext, "speak, friend, and enter," becomes HLAXCWJEANGXNGANGAJ, ignoring commas and spaces. The whole key space is quite big. There are 26×25×24×23×…×two×1 possible keys. This is written as 26!, read "twenty-six factorial." 26! is near equal to ii88, which is large plenty to resist fauna-force attacks that effort all the possible keys; that is, it satisfies the sufficient central space principle. But that does not mean the algorithm resists all attempts to subvert it.

The mono-alphabetic zero is discipline to frequency attacks or guessing. The ciphertext has but every bit many 'A' characters every bit there are 'due east' characters in the plaintext. Anyone trying to attack the ciphertext could use a table of the frequency of letters in the English linguistic communication to make some smart guesses nigh which ciphertext characters are which plaintext characters. This succeeds relatively easily. Humans can practice it, rather slowly, once they accept about x words, sometimes less. This is a relatively common puzzle in newspapers, so it should not exist surprising it's easy to intermission. Computers can also do it reliably when they take at least 150 characters [6, p. 131].

Frequency attacks are not limited to single letters. The trouble applies to modern systems as well. If a bank begins every transaction with the same 10 characters, and then an adversary would rightfully judge that that string is more frequent. Modernistic algorithms effort to be robust against this in a variety of ways, which volition be discussed later. However, sometimes the best course of activity for the defender to resist such frequency attacks is for the defender to modify the contents of the actual message, before encryption, to remove these regularities. If that is not possible, regularities in the plaintext should be minimized.

Ane method of frustrating frequency attacks on the underlying plaintext is to increase the block size of the cipher. The block size is how many units (in our example characters) are encrypted at once. Both the Caesar nil and the mono-alphabetic substitution have a block size of ane—only one character is encrypted at a time. A different defense force is to use a key that changes per element of plaintext, whether or not the block size increases. The number of changes in the key per element of plaintext before the key repeats is called the catamenia of the fundamental; both preceding cipher examples have a key period of i as well as a block size of 1. Cake ciphers are ciphers with a cake size greater than 1, and they will be discussed in more detail in the context of modern encryption in the section "Block Ciphers". Withal, before moving to the discussion of transposition ciphers, nosotros will talk over one more substitution cipher: ane with a key period of capricious length.

The Vigenère cipher, or polyalphabetic shift naught, was invented in 16th- century France, and for many centuries was considered unbreakable. Instead of choosing a unmarried letter of the alphabet as the key, we choose a word or random string of letters. The encryption per character is the same as the Caesar cipher—letters are converted to numbers and added. When the last letter of the key has been used, the algorithm loops dorsum to the beginning of the key and starts again, and so on, until it reaches the cease of the message. For instance:

Plaintext: speak, friend, and enter

Key: FRODO

Ciphertext: XFSDYE WELSSUN DAI VAWSW

To encrypt, use the first letter of the alphabet s+F=X, the second letter p+R=F, the third letter eastward+O=South, and so on. On the sixth graphic symbol nosotros attain the end of the key, and so go dorsum to the beginning of the key to compute ,+F=E, followed by f+R=West, and then on. The zilch is conceptually like using multiple unlike mono-alphabetic cipher keys in sequence.

In this instance, the letter e in the plaintext is variably encrypted to S and V, and in the ciphertext W is, in different places, the result of a plaintext f, t, and r. This variability makes attacking the ciphertext by the frequency of messages in English language much more difficult. Notation a feature of the math here that did not arise in the previous case. The letter of the alphabet P is 15, R is 17, and and so 15+17=32. Nevertheless, 32 is greater than the value of a comma, 26, the final character in our alphabet. To bring 32 back into our ring of numbers, nosotros subtract past the number of characters we have (27) and then convert the answer to the alphabetic character F. What mathematicians use to be rigorous about this is the modulus operator, which uses the "mod" symbol, %. So we write 32 % 27=5, read "32 modulo 27" or "32 mod 27" for short. The functioning is technically to carve up by 27 so take the whole number remainder that is left. Information technology comes up a lot in cryptography, simply that is all that needs to exist said about information technology for now.

The Vigenère cipher is still brittle, although it is harder. If the antagonist knows the key period, frequency attacks are possible on each unit that uses the same key. And in the mid-19th century a robust method for discovery of the key menses of the goose egg was developed. This trouble persists to this solar day. The Vigenère nada is an example of a stream goose egg. Modern stream ciphers are discussed in a post-obit section. However, the general method for fugitive this problem has just been to make a key period that is long plenty that it substantially never repeats, and if it does repeat, to get-go using a new key. There is no skilful algorithmic fashion effectually the trouble of brusque cardinal periods—in one case it starts to repeat, the cipher is breakable.

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Exchange Transport and Routing

Tony Redmond , in Microsoft Exchange Server 2007 with SP1, 2008

6.2.one Hidden administrative and routing groups

Of course, it is difficult to move from one transport compages to another without leaving some traces behind. In the instance of Substitution 2007, the designers had to back up backwards compatibility with routing and administrative groups to permit Exchange 2007 servers to co-exist inside an organization with Exchange 2003 servers. The solution was to create a hidden administrative grouping and a subconscious routing group to hold Exchange 2007 servers every bit they were installed into the organization. You lot can run across the subconscious groups if you lot examine the details of the Substitution organization through the Agile Directory or look at them through ESM. A minor but important item was to come with a suitable name for the hidden administrative and routing groups, and the Substitution designers decided to call them:

On the surface, information technology looks as if the designers used the same algorithm as is used to generate the alphanumeric keys for Windows licenses, but the petty pursuit answer is that they used a uncomplicated Caesar cipher. two Thus, the actual meaning of the names are:

F E D Due east
Y X W X
D C B C
I H G H
B A Z A
O N M North
H G F Thou
F E D East
2 1 0 i
iii 2 1 2
South R Q R
P O N O
D C B C
Fifty K J K
T Due south R Southward

All of this goes to show that at least some humor was applied during the design of Exchange 2007.

Later you install Exchange 2007 into an Exchange 2003 organization, the installation process updates the ESM console to prevent you renaming the special administrative and routing groups. Some administrators have asked if it is possible to alter the proper noun of the special administrative and routing groups because the names, while cute, are somewhat impuissant, especially if you want to use LDAP to interrogate the directory. It is obviously much easier (and less probable to make a mistake) to type in a proper name like "Ex2007Admin" instead of "Commutation Administrative Group (FYDIBOHF23SPDLT)." The special names aren't simply in a few places as they are scattered beyond the Agile Directory in apply in LegacyExchangeDN properties for many objects. Microsoft'southward answer is that information technology is impossible to modify the names because they are hard-coded in some places like the setup programme, which expects to install servers into the special administrative group.

Annotation that the creation of the hidden administrative and routing groups to back up Substitution 2007 servers volition effect in a full OAB download for whatever client like Outlook 2000 or XP that uses OAB format 2 or three.

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Anti-forensics

John Sammons , in The Basics of Digital Forensics (2d Edition), 2015

Early on encryption

Encryption itself isn't a by-production of computer technology alone. It's been around for thousands of years in 1 form or another. One of the earliest and best-known encryption schemes is the Caesar Nix. The Caesar Cipher is a shift cypher and encrypts the data by replacing the original letters with "x" number of characters alee in the alphabet. For example, using the Caesar Zilch and a key of five, an "A" would become an "F." Tabular array half-dozen.i shows the entire alphabet both as plain text and as cipher text after the same nil has been applied. Notation that each letter has been shifted five spaces below or past its original position.

Table vi.1. The Alphabet with Simple Encryption (Caesar Cipher). The Key in This Case is V.

Apparently text A B C D Due east F G H I J K L G N O P Q R S T U Five W X Y Z
Cipher text F Thousand H I J K L M N O P Q R S T U 5 Due west X Y Z A B C D E

Now let's encrypt "forensics" using the Caesar Cipher with a key of 8. Table 6.ii shows us the conversion of Plainly Text to cipher text.

Table 6.ii. A Letter-by-Alphabetic character Conversion Using the Caesar Cipher and a Key of Eight

Apparently text F O R Due east N S I C S
Zero text N W Z M 5 A Q K A

This simple process is nevertheless employed today. It's ofttimes used to obfuscate computer lawmaking. At showtime glance, it appears that the terms encryption and obfuscate are interchangeable. They are similar plenty to sometimes be confused, simply the differences are meaning plenty to merit clarification. Obfuscation and encryption are both intended to make things harder to understand. Obfuscation, nevertheless, is used to protect computer lawmaking, rather than the information itself (Tyma, 2003). Obfuscation also protects lawmaking from reverse engineering. Encryption tin can't be used in this manner because information technology would render the lawmaking totally unreadable to the computer.

ROT13 is a modern version of the Caesar Nothing in apply today for obfuscation. In ROT13, letters are shifted by 13 positions. In this scheme, an "A" becomes an "N" and and then on. Table 6.3 shows an excerpt from Lincoln'due south Gettysburg Address afterwards ROT13 has been practical.

Tabular array vi.3. The Opening of Lincoln's Gettysburg Address Encrypted Using ROT13

Fourscore and seven years ago our fathers brought forth on this
Sbhefpber naq frira lrnef ntb bhe snguref oebhtug sbegu ba guvf
continent a new nation conceived in liberty and dedicated
pbagvarag n arj angvba pbaprvirq va yvoregl naq qrqvpngrq
to the proposition that all men are created equal
gb gur cebcbfvgvba gung nyy zra ner perngrq rdhny

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