Base64

The term Base64 refers to a specific MIME content transfer encoding. It is also used as a generic term for any similar encoding scheme that encodes binary data by treating it numerically and translating it into a base 64 representation. The particular choice of base is due to the history of character set encoding: one can choose 64 characters that are both part of the subset common to most encodings, and also printable. This combination leaves the data unlikely to be modified in transit through systems, such as email, which were traditionally not 8-bit clean.
The precise choice of characters is difficult. The earliest instances of this type of encoding were created for dialup communication between systems running the same OS - e.g. Uuencode for UNIX, BinHex for the TRS-80 (later adapted for the Macintosh) - and could therefore make more assumptions about what characters were safe to use. For instance, Uuencode uses uppercase letters, digits, and many punctuation characters, but no lowercase, since UNIX was sometimes used with terminals that did not support distinct letter case. Unfortunately for interoperability with non-UNIX systems, some of the punctuation characters do not exist in other traditional character sets. The MIME Base64 encoding replaces most of the punctuation characters with the lowercase letters, a reasonable requirement by the time it was designed.
MIME Base64 uses A–Z, a–z, and 0–9 for the first 62 digits. There are other similar systems, usually derived from Base64, that share this property but differ in the symbols chosen for the last two digits; an example is UTF-7.
A quote from Thomas Hobbes's Leviathan:
Man is distinguished, not only by his reason, but by this singular passion from other animals, which is a lust of the mind, that by a perseverance of delight in the continued and indefatigable generation of knowledge, exceeds the short vehemence of any carnal pleasure.
is encoded in MIME's base64 scheme as follows:
TWFuIGlzIGRpc3Rpbmd1aXNoZWQsIG5vdCBvbmx5IGJ5IGhpcyByZWFzb24sIGJ1dCBieSB0aGlz
IHNpbmd1bGFyIHBhc3Npb24gZnJvbSBvdGhlciBhbmltYWxzLCB3aGljaCBpcyBhIGx1c3Qgb2Yg
dGhlIG1pbmQsIHRoYXQgYnkgYSBwZXJzZXZlcmFuY2Ugb2YgZGVsaWdodCBpbiB0aGUgY29udGlu
dWVkIGFuZCBpbmRlZmF0aWdhYmxlIGdlbmVyYXRpb24gb2Yga25vd2xlZGdlLCBleGNlZWRzIHRo
ZSBzaG9ydCB2ZWhlbWVuY2Ugb2YgYW55IGNhcm5hbCBwbGVhc3VyZS4=
In the above quote the encoded value of Man is TWFu. Encoded in ASCII, M, a, n are stored as the bytes 77, 97, 110, which are 01001101, 01100001, 01101110 in base 2. These three bytes are joined together in a 24 bit buffer producing 010011010110000101101110. Packs of 6 bits (6 bits has a maximum of 64 different binary values) are converted into 4 numbers (24 = 6x4) which are then converted to their corresponding values in Base 64.

As this example illustrates, Base 64 encoding converts 3 uncoded bytes (in this case, ASCII characters) into 4 encoded ASCII characters.
The example below illustrates how shortening the input changes the output padding:
Input ends with: carnal pleasure. Output ends with: c3VyZS4=
Input ends with: carnal pleasure Output ends with: c3VyZQ==
Input ends with: carnal pleasur Output ends with: c3Vy
Input ends with: carnal pleasu Output ends with: c3U=
Note that the same characters will be encoded differently depending on their position within the three-octet group which is encoded to produce the four characters. For example
The Input: leasure. Encodes to bGVhc3VyZS4=
The Input: easure. Encodes to ZWFzdXJlLg==
The Input: asure. Encodes to YXN1cmUu
The Input: sure. Encodes to c3VyZS4=

Baconian Cipher

Bacon's cipher or the Baconian cipher is a method of steganography (a method of hiding a secret message as opposed to a true cipher) devised by Francis Bacon. A message is concealed in the presentation of text, rather than its content.
To encode a message, each letter of the plain text is replaced by a group of five of the letters 'A' or 'B'. This replacement is done according to the alphabet of the Baconian cipher, shown below.
a AAAAA g AABBA n ABBAA t BAABA
b AAAAB h AABBB o ABBAB u-v BAABB
c AAABA i-j ABAAA p ABBBA w BABAA
d AAABB k ABAAB q ABBBB x BABAB
e AABAA l ABABA r BAAAA y BABBA
f AABAB m ABABB s BAAAB z BABBB
The writer must make use of two different typefaces for this cipher. After preparing a false message with the same number of letters as all of the As and Bs in the real, secret message, two typefaces are chosen, one to represent As and the other Bs. Then each letter of the false message must be presented in the appropriate typeface, according to whether it stands for an A or a B.
To decode the message, the reverse method is applied. Each "typeface 1" letter in the false message is replaced with an A and each "typeface 2" letter is replaced with a B. The Baconian alphabet is then used to recover the original message.
Any method of writing the message that allows two distinct representations for each character can be used for the Bacon Cipher. Bacon himself prepared a Biliteral Alphabet for handwritten capital and small letters with each having two alternative forms, one to be used as A and the other as B. This was published as an illustrated plate in his De Augmentis Scientiarum (The Advancement of Learning).
Because any message of the right length can be used to carry the encoding, the secret message is effectively hidden in plain sight. The false message can be on any topic and thus can distract a person seeking to find the real message.
Some people have suggested that the plays attributed to William Shakespeare were in fact written by Francis Bacon, and that the published plays contain enciphered messages to that effect. Both Ignatius L. Donnelly and Elizabeth Wells Gallup attempted to find such messages by looking for the use of Bacon's cipher in early printed editions of the plays.
A further theory based on Bacon's cipher was published by Edward Clark referring to an inscription on Shakespeare's funerary monument which used a mixture of letter-shapes. Unfortunately the stone had crumbled and been replaced more than half a century earlier, so Clark had to rely on copies. He was building on an article by Hugh Black suggesting that the inscription concealed the sentence, "FRA BA WRT EAR AY", an abbreviation of "Francis Bacon wrote Shakespeare's plays."

Affine Cipher

The Affine cipher is a special case of the more general monoalphabetic substitution cipher. In affine ciphers the encryption function for a letter is e(x) = (ax + b)(mod m) where,
• a and m are coprime (otherwise a would have no multiplicative inverse modulo m).
• m is the size of the alphabet.
The decryption function is d(x) = a − 1(e(x) − b)(mod m) where a − 1 is the multiplicative inverse of a in the group
Considering the specific case of encrypting messages in English (i.e. m = 26), there are a total of 286 non-trivial affine ciphers, not counting the trivial Caesar ciphers obtained when a = 1. This lack of variety renders the system as highly insecure when considered in light of Kerckhoffs' Principle. Even without foreknowledge that a text were enciphered with an affine cipher, the ciphertext would have all of the vulnerabilities of ordinary monoalphabetic substitution ciphers.
The cipher's primary weakness comes from the fact that if the cryptanalyst can discover (by means of frequency analysis, brute force, guessing or otherwise) the plaintext of two ciphertext characters then the key can be obtained by solving a simultaneous equation. Since we know a and m are relatively prime this can be used to rapidly discard many "false" keys in an automated system.
The same type of transformation used in affine ciphers is used in linear congruential generators, a type of pseudorandom number generator. This generator is not a cryptographically secure pseudorandom number generator for the same reason that the affine cipher is not secure.

ASCII Chart

I was looking for an ASCII Chart with its Binary and I found one from http://www.pcguide.com/res/tablesASCII-c.html

Take a look at it, its very complete and helpful.

Playfair Cipher

The Playfair cipher or Playfair square is a manual symmetric encryption technique and was the first literal digraph substitution cipher. The scheme was invented in 1854 by Charles Wheatstone, but bears the name of Lord Playfair who promoted the use of the cipher.

The technique encrypts pairs of letters (digraphs), instead of single letters as in the simple substitution cipher and rather more complex Vigenère cipher systems then in use. The Playfair is thus significantly harder to break since the frequency analysis used for simple substitution ciphers does not work with it. Frequency analysis can still be undertaken, but on the 600 possible digraphs rather than the 26 possible monographs. The frequency analysis of digraphs is possible, but considerably more difficult – and it generally requires a much larger ciphertext in order to be useful.

HISTORY

Despite its invention by Wheatstone, it became known as the Playfair cipher after Lord Playfair, who heavily promoted its use.

The first recorded description of the Playfair cipher was in a document signed by Wheatstone on 26 March 1854.

It was rejected by the British Foreign Office when it was developed because of its perceived complexity. When Wheatstone offered to demonstrate that three out of four boys in a nearby school could learn to use it in 15 minutes, the Under Secretary of the Foreign Office responded, "That is very possible, but you could never teach it to attachés."

It was used for tactical purposes by British forces in the Second Boer War and in World War I and for the same purpose by the Australians and Germans during World War II. This was because Playfair is reasonably fast to use and requires no special equipment. A typical scenario for Playfair use would be to protect important but non-critical secrets during actual combat. By the time the enemy cryptanalysts could break the message, the information was useless to them.

Playfair is no longer used by military forces because of the advent of digital encryption devices. Playfair is now regarded as insecure for any purpose because modern hand-held computers could easily break the cipher within seconds.

The first published solution of the Playfair cipher was described in a 19-page pamphlet by Lieutenant Joseph O. Mauborgne, published in 1914.

USING PLAYFAIR CIPHER

The Playfair cipher uses a 5 by 5 table containing a key word or phrase. Memorization of the keyword and 4 simple rules was all that was required to create the 5 by 5 table and use the cipher.

To generate the key table, one would first fill in the spaces in the table with the letters of the keyword (dropping any duplicate letters), then fill the remaining spaces with the rest of the letters of the alphabet in order (usually omitting "Q" to reduce the alphabet to fit, other versions put both "I" and "J" in the same space). The key can be written in the top rows of the table, from left to right, or in some other pattern, such as a spiral beginning in the upper-left-hand corner and ending in the center. The keyword together with the conventions for filling in the 5 by 5 table constitute the cipher key.

To encrypt a message, one would break the message into digraphs (groups of 2 letters) such that, for example, "HelloWorld" becomes "HE LL OW OR LD", and map them out on the key table. The two letters of the digraph look like the corners of a rectangle in the key table. Note the relative position of the corners of this rectangle. Then apply the following 4 rules, in order, to each pair of letters in the plaintext:

* If both letters are the same (or only one letter is left), add an "X" after the first letter. Encrypt the new pair and continue. Some variants of Playfair use "Q" instead of "X", but any uncommon monograph will do.
* If the letters appear on the same row of your table, replace them with the letters to their immediate right respectively (wrapping around to the left side of the row if a letter in the original pair was on the right side of the row).
* If the letters appear on the same column of your table, replace them with the letters immediately below respectively (wrapping around to the top side of the column if a letter in the original pair was on the bottom side of the column).
* If the letters are not on the same row or column, replace them with the letters on the same row respectively but at the other pair of corners of the rectangle defined by the original pair. The order is important – the first encrypted letter of the pair is the one that lies on the same row as the first plaintext letter.

To decrypt, use the inverse of these 4 rules (dropping any extra "X"s (or "Q"s) that don't make sense in the final message when you finish).

Using "playfair example" as the key, the table becomes:

P L A Y F
I R E X M
B C D G H
J K N O S
T U V W Z

Encrypting the message "Hide the gold in the tree stump":

HI DE TH EG OL DI NT HE TR EX ES TU MP


1. The pair HI forms a rectangle, replace it with BM
2. The pair DE is in a column, replace it with ND
3. The pair TH forms a rectangle, replace it with ZB
4. The pair EG forms a rectangle, replace it with XD
5. The pair OL forms a rectangle, replace it with KY
6. The pair DI forms a rectangle, replace it with BE
7. The pair NT forms a rectangle, replace it with JV
8. The pair HE forms a rectangle, replace it with DM
9. The pair TR forms a rectangle, replace it with UI
10. The pair EX (X inserted to split EE) is in a row, replace it with XM
11. The pair ES forms a rectangle, replace it with MN
12. The pair TU is in a row, replace it with UV
13. The pair MP forms a rectangle, replace it with IF

BM ND ZB XD KY BE JV DM UI XM MN UV IF

Thus the message "Hide the gold in the tree stump" becomes "BMNDZBXDKYBEJVDMUIXMMNUVIF".

Assume one wants to encrypt the digraph OR. There are three general cases:

1)

* * * * *
* O Y R Z
* * * * *
* * * * *
* * * * *

Hence, OR -> YZ

2)

* * O * *
* * B * *
* * * * *
* * R * *
* * Y * *

Hence, OR -> BY

3)

Z * * O *
* * * * *
* * * * *
R * * X *
* * * * *

Hence, OR -> ZX

Like most pre-modern era ciphers, the Playfair cipher can be easily cracked if there is enough text. Obtaining the key is relatively straightforward if both plaintext and ciphertext are known. When only the ciphertext is known, brute force cryptanalysis of the cipher involves searching through the key space for matches between the frequency of occurrence of digrams (pairs of letters) and the known frequency of occurrence of digrams in the assumed language of the original message.

Cryptanalysis of Playfair is similar to that of four-square and two-square ciphers, though the relative simplicity of the Playfair system makes identifying candidate plaintext strings easier. Most notably, a Playfair digraph and its reverse (e.g. AB and BA) will decrypt to the same letter pattern in the plaintext (e.g. RE and ER). In English, there are many words which contain these reversed digraphs such as REceivER and DEpartED. Identifying nearby reversed digraphs in the ciphertext and matching the pattern to a list of known plaintext words containing the pattern is an easy way to generate possible plaintext strings with which to begin constructing the key.

A different approach to tackling a Playfair cipher is the shotgun hill climbing method. This starts with a random square of letters. Then minor changes are introduced (i.e. switching letters, rows, or reflecting the entire square) to see if the candidate plaintext is more like standard plaintext than before the change (perhaps by comparing the trigrams to a known frequency chart). If the new square is deemed to be an improvement, then it is adopted and then further mutated to find an even better candidate. Eventually, the plaintext or something very close is found to achieve a maximal score by whatever grading method is chosen. This is obviously beyond the range of typical human patience, but computers can adopt this algorithm to crack Playfair ciphers with a relatively small amount of text.

Another aspect of Playfair that separates it from four-square and two-square ciphers is the fact that it will never contain a double-letter digraph, e.g. EE. If there are no double letter digraphs in the ciphertext and the length of the message is long enough to make this statistically significant, it is very likely that the method of encryption is Playfair.

A good tutorial on reconstructing the key for a Playfair cipher can be found in chapter 7, "Solution to Polygraphic Substitution Systems," of Field Manual 34-40-2, produced by the United States Army.

A detailed cryptanalysis of Playfair is undertaken in chapter 28 of Dorothy L. Sayers' mystery novel Have His Carcase. In this story, a Playfair message is demonstrated to be cryptographically weak as the detective is able to solve for the entire key making only a few guesses as to the formatting of the message (in this case, that the message starts with the name of a city and then a date). Sayers' book includes a detailed description of the mechanics of Playfair encryption as well as a step-by-step account of manual cryptanalysis.

The German Army, Air Force and Police used the Double Playfair system as a medium-grade cipher in WWII, but as they had broken the cipher early in WWI, they adapted it by introducing a second square from which the second letter of each bigram was selected, and dispensed with the keyword, placing the letters in random order. But with the German fondness for ‘pro forma’ messages, they were broken at Bletchley Park. Messages were preceded by a sequential number, and numbers were spelt out. As the German numbers 1 (eins) to twelve (zwölf) contain all but eight of the letters in the Double Playfair squares, pro forma traffic was relatively easy to break (Smith, page 74-75)

Caesar Cipher

In cryptography, a Caesar cipher, also known as a Caesar's cipher, the shift cipher, Caesar's code or Caesar shift, is one of the simplest and most widely known encryption techniques. It is a type of substitution cipher in which each letter in the plaintext is replaced by a letter some fixed number of positions down the alphabet. For example, with a shift of 3, A would be replaced by D, B would become E, and so on. The method is named after Julius Caesar, who used it to communicate with his generals.

The encryption step performed by a Caesar cipher is often incorporated as part of more complex schemes, such as the Vigenère cipher, and still has modern application in the ROT13 system. As with all single alphabet substitution ciphers, the Caesar cipher is easily broken and in practice offers essentially no communication security.

The transformation can be represented by aligning two alphabets; the cipher alphabet is the plain alphabet rotated left or right by some number of positions. For instance, here is a Caesar cipher using a left rotation of three places (the shift parameter, here 3, is used as the key):

Plain: ABCDEFGHIJKLMNOPQRSTUVWXYZ
Cipher: DEFGHIJKLMNOPQRSTUVWXYZABC

To encrypt a message, simply look up each letter of the message in the "plain" line and write down the corresponding letter in the "cipher" line. To decipher, do the reverse.

Plaintext: the quick brown fox jumps over the lazy dog
Ciphertext: WKH TXLFN EURZQ IRA MXPSV RYHU WKH ODCB GRJ

e encryption can also be represented using modular arithmetic by first transforming the letters into numbers, according to the scheme, A = 0, B = 1,..., Z = 25. Encryption of a letter x by a shift n can be described mathematically as,


(Note, there are different definitions for the modulo operation. In the above, the result is in the range 0...25. I.e., if x+n or x-n are not in the range 0...25, we have to subtract or add 26.)

The replacement remains the same throughout the message, so the cipher is classed as a type of monoalphabetic substitution, as opposed to polyalphabetic substitution.

HISTORY

The Caesar cipher is named after Julius Caesar, who, according to Suetonius, used it with a shift of three to protect messages of military significance. While Caesar's was the first recorded use of this scheme, other substitution ciphers are known to have been used earlier.

If he had anything confidential to say, he wrote it in cipher, that is, by so changing the order of the letters of the alphabet, that not a word could be made out. If anyone wishes to decipher these, and get at their meaning, he must substitute the fourth letter of the alphabet, namely D, for A, and so with the others.

It is unknown how effective the Caesar cipher was at the time, but it is likely to have been reasonably secure, not least because most of Caesar's enemies would have been illiterate and others would have assumed that the messages were written in an unknown foreign language.[4] Assuming that an attacker could read the message, there is no record at that time of any techniques for the solution of simple substitution ciphers. The earliest surviving records date to the 9th century works of Al-Kindi in the Arab world with the discovery of frequency analysis.

A Caesar cipher with a shift of one is used on the back of the Mezuzah to encrypt the names of God. This may be a hangover from an earlier time when Jewish people were not allowed to have Mezuzahs. The letters of the cryptogram themselves comprise a divine name which keeps the forces of evil in check.

In the 19th century, the personal advertisements section in newspapers would sometimes be used to exchange messages encrypted using simple cipher schemes. Kahn (1967) describes instances of lovers engaging in secret communications enciphered using the Caesar cipher in The Times.[7] Even as late as 1915, the Caesar cipher was in use: the Russian army employed it as a replacement for more complicated ciphers which had proved to be too difficult for their troops to master; German and Austrian cryptanalysts had little difficulty in decrypting their messages.

Caesar ciphers can be found today in children's toys such as secret decoder rings. A Caesar shift of thirteen is also performed in the ROT13 algorithm, a simple method of obfuscating text widely found in UNIX and used to obscure text (such as joke punchlines and story spoilers), but not used as a method of encryption.

The Vigenère cipher uses a Caesar cipher with a different shift at each position in the text; the value of the shift is defined using a repeating keyword. If a single-use keyword is as long as the message and chosen randomly then this is a one-time pad cipher, unbreakable if the users maintain the keyword's secrecy. Keywords shorter than the message (e.g., "Complete Victory" used by the Confederacy during the American Civil War), introduce a cyclic pattern that might be detected with a statistically advanced version of frequency analysis.

In April 2006, fugitive Mafia boss Bernardo Provenzano was captured in Sicily partly because of cryptanalysis of his messages written in a variation of the Caesar cipher. Provenzano's cipher used numbers, so that "A" would be written as "4", "B" as "5", and so on.

BREAKING THE CIPHER

The Caesar cipher can be easily broken even in a ciphertext-only scenario. Two situations can be considered:

1. an attacker knows (or guesses) that some sort of simple substitution cipher has been used, but not specifically that it is a Caesar scheme;
2. an attacker knows that a Caesar cipher is in use, but does not know the shift value.

In the first case, the cipher can be broken using the same techniques as for a general simple substitution cipher, such as frequency analysis or pattern words. While solving, it is likely that an attacker will quickly notice the regularity in the solution and deduce that a Caesar cipher is the specific algorithm employed.

In the second instance, breaking the scheme is even more straightforward. Since there are only a limited number of possible shifts (26 in English), they can each be tested in turn in a brute force attack. One way to do this is to write out a snippet of the ciphertext in a table of all possible shifts — a technique sometimes known as "completing the plain component". The example given is for the ciphertext "EXXEGOEXSRGI"; the plaintext is instantly recognisable by eye at a shift of four. Another way of viewing this method is that, under each letter of the ciphertext, the entire alphabet is written out in reverse starting at that letter. This attack can be accelerated using a set of strips prepared with the alphabet written down them in reverse order. The strips are then aligned to form the ciphertext along one row, and the plaintext should appear in one of the other rows.

Another brute force approach is to match up the frequency distribution of the letters. By graphing the frequencies of letters in the ciphertext, and by knowing the expected distribution of those letters in the original language of the plaintext, a human can easily spot the value of the shift by looking at the displacement of particular features of the graph. This is known as frequency analysis. For example in the English language the plaintext frequencies of the letters E, T, (usually most frequent), and Q, Z (typically least frequent) are particularly distinctive.

Computers can also do this by measuring how well the actual frequency distribution matches up with the expected distribution; for example, the chi-square statistic can be used.

For natural language plaintext, there will, in all likelihood, be only one plausible decryption, although for extremely short plaintexts, multiple candidates are possible. For example, the ciphertext MPQY could, plausibly, decrypt to either "aden" or "know" (assuming the plaintext is in English); similarly, "ALIIP" to "dolls" or "wheel"; and "AFCCP" to "jolly" or "cheer" (see also unicity distance).

Multiple encryptions and decryptions provide no additional security. This is because two encryptions of, say, shift A and shift B, will be equivalent to an encryption with shift A + B. In mathematical terms, the encryption under various keys forms a group.

Conclusion = The cipher could be cracked by doing the parameter one by one, for example:

Decryption
Shift Candidate plaintext
0 exxegoexsrgi
1 dwwdfndwrqfh
2 cvvcemcvqpeg
3 buubdlbupodf
4 attackatonce
5 zsszbjzsnmbd
6 yrryaiyrmlac

Until

23 haahjrhavujl
24 gzzgiqgzutik
25 fyyfhpfytshj

What is a Cipher?

In cryptography, a cipher (or cypher) is an algorithm for performing encryption and decryption — a series of well-defined steps that can be followed as a procedure. An alternative term is encipherment. In non-technical usage, a “cipher” is the same thing as a “code”; however, the concepts are distinct in cryptography. In classical cryptography, ciphers were distinguished from codes. Codes operated by substituting according to a large codebook which linked a random string of characters or numbers to a word or phrase. For example, “UQJHSE” could be the code for “Proceed to the following coordinates”. When using a cipher the original information is known as plaintext, and the encrypted form as ciphertext. The ciphertext message contains all the information of the plaintext message, but is not in a format readable by a human or computer without the proper mechanism to decrypt it; it should resemble random gibberish to those not intended to read it.

The operation of a cipher usually depends on a piece of auxiliary information, called a key or, in traditional NSA parlance, a cryptovariable. The encrypting procedure is varied depending on the key, which changes the detailed operation of the algorithm. A key must be selected before using a cipher to encrypt a message. Without knowledge of the key, it should be difficult, if not nearly impossible, to decrypt the resulting cipher into readable plaintext.

Most modern ciphers can be categorized in several ways:

* By whether they work on blocks of symbols usually of a fixed size (block ciphers), or on a continuous stream of symbols (stream ciphers).
* By whether the same key is used for both encryption and decryption (symmetric key algorithms), or if a different key is used for each (asymmetric key algorithms). If the algorithm is symmetric, the key must be known to the recipient and to no one else. If the algorithm is an asymmetric one, the encyphering key is different from, but closely related to, the decyphering key. If one key cannot be deduced from the other, the asymmetric key algorithm has the public/private key property and one of the keys may be made public without loss of confidentiality. The Feistel cipher uses a combination of substitution and transposition techniques. Most block cipher algorithms are based on this structure.

Cipher” (Middle French as cifre and Medieval Latin as cifra, from the Arabic sifr = zero) is alternatively spelled “cypher” (however, this variant is now uncommon); similarly “ciphertext” and “cyphertext”, and so forth.

The word “cipher” in former times meant “zero” and had the same origin (see Zero — Etymology), and later was used for any decimal digit, even any number. There are these theories about how the word “cipher” may have come to mean encoding:

* Encoding often involved numbers.
* The Roman number system was very cumbersome because there was no concept of zero (or empty space). The concept of zero (which was also called “cipher”), which we all now think of as natural, was very alien in medieval Europe, so confusing and ambiguous to common Europeans that in arguments people would say “talk clearly and not so far fetched as a cipher”. Cipher came to mean concealment of clear messages or encryption.
o The French formed the word “chiffre” and adopted the Italian word “zero”.
o The English used “zero” for “0”, and “cipher” from the word “ciphering” as a means of computing.
o The Germans used the words “Ziffer” (digit, “Zahl”) and “Chiffre”.

Dr. Al-Kadi (ref-3) concluded that the Arabic word sifr, for the digit zero, developed into the European technical term for encryption.

PS : To understand more about ciphers, I will give some posts about it.

In Conclusion : A cipher is the art of Encryption and Decryption. Breaking a cipher is way more harder then breaking a password. A Password which takes 3 days to crack, a Cipher would take more than days to crack, depending on the Cipher. The easiest Cipher that could be cracked is Caesar Cipher, the cipher is based on shifting words by a parameter. Caesar Cipher could be cracked easily and normally it takes up to 10 minutes to crack a Caesar Cipher Ciphertext on a computer. A Plaintext could be assumed as the 'Text to encrypt', while Ciphertext means the Plaintext which has been encrypted or ciphered. For example, in Caesar Cipher, Plaintext "the quick brown fox jumps over the lazy dog" in parameter 3 would be: "WKH TXLFN EURZQ IRA MXPSV RYHU WKH ODCB GRJ" on the Ciphertext.

This way, Cipher or Encryption and Decryption is harder or easier to crack (most of them is harder).