In cryptography, a cipher is an algorithm for performing encryption or decryption—a series of well-defined steps that can be followed as a procedure. An alternative, less common term is encipherment. To encipher or encode is to convert information into cipher or code. In common parlance, "cipher" is synonymous with "code", as they are both a set of steps that encrypt a message. Codes substitute different length strings of character in the output, while ciphers substitute the same number of characters as are input. There are exceptions and some cipher systems may use more, or fewer, characters when output versus the number that were input. 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, 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.

The operation of a cipher depends on a piece of auxiliary information, called a key. 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 impossible, to decrypt the resulting ciphertext into readable plaintext. Most modern ciphers can be categorized in several ways By whether they work on blocks of symbols of a fixed size, or on a continuous stream of symbols. By whether the same key is used for both encryption and decryption, or if a different key is used for each. If the algorithm is symmetric, the key must be known to no one else. If the algorithm is an asymmetric one, the enciphering key is different from, but related to, the deciphering 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 word "cipher" in former times meant "zero" and had the same origin: Middle French as cifre and Medieval Latin as cifra, from the Arabic صفر sifr = zero. "Cipher" was used for any decimal digit any number. There are many theories about how the word "cipher" may have come to mean "encoding". Encoding involved numbers; the Roman number system was cumbersome because there was no concept of zero. The concept of zero, now common knowledge, was alien to medieval Europe, so confusing and ambiguous to common Europeans that in arguments people would say "talk and not so far fetched as a cipher". Cipher came to mean concealment of clear messages or encryption; the French formed the word "chiffre" and adopted the Italian word "zero". The English used "zero" for "0", "cipher" from the word "ciphering" as a means of computing; the Germans used the words "Ziffer" and "Chiffre". The Dutch still use the word "cijfer" to refer to a numerical digit; the Slovaks also sometimes use the word "cifra" to refer to a numerical digit, they use word "číslo" for a number.

The Bosnians and Serbians use the word "cifra", which refers to a digit, or in some cases, any number. Besides "cifra", they use word "broj" for a number; the Italians and the Spanish use the word "cifra" to refer to a digit. The Swedes use the word "siffra" which refers to a digit, "chiffer"; the Greeks use the word "τζίφρα" to refer to a hard-to-read signature one written with a single stroke of the pen. Ibrahim Al-Kadi concluded that the Arabic word sifr, for the digit zero, developed into the European technical term for encryption; as the decimal zero and its new mathematics spread from the Arabic world to Europe in the Middle Ages, words derived from sifr and zephirum came to refer to calculation, as well as to privileged knowledge and secret codes. According to Ifrah, "in thirteenth-century Paris, a'worthless fellow' was called a'... cifre en algorisme', i.e. an'arithmetical nothing'." Cipher was the European pronunciation of sifr, cipher came to mean a message or communication not understood.

In non-technical usage, a " code" means a "cipher". Within technical discussions, the words "code" and "cipher" refer to two different concepts. Codes work at the level of meaning—that is, words or phrases are converted into something else and this chunking shortens the message. An example of this is the Commercial Telegraph Code, used to shorten long telegraph messages which resulted from entering into commercial contracts using exchanges of Telegrams. Another example is given by whole word ciphers, which allow the user to replace an entire word with a symbol or character, much like the way Japanese utilize Kanji characters to supplement their language. Ex "The quick brown fox jumps over the lazy dog" becomes "The quick brown 狐 jumps 过 the lazy 狗". Ciphers, on the other hand, work at a lower level: the level of individual letters, small groups of letters, or, in modern schemes, individual bits and blocks of bits; some systems used both codes and ciphers in one system, using superencipherment to increase the security.

In some cases the terms codes and ciphers are used synonymously to subst

Lesser goldfinch

The lesser goldfinch is a small songbird of the Americas. Together with its relatives the American goldfinch and Lawrence's goldfinch, it forms the American goldfinches clade in the genus Spinus sensu stricto; the American goldfinches can be distinguished by the males having a black forehead, whereas the latter is red or yellow in the European goldfinch and its relatives. North American males are markedly polymorphic and 5 subspecies are named; this petite species is not only the smallest North American Spinus finch, it may be the smallest true finch in the world. Some sources list more subtropical Spinus species as smaller on average, including the Andean siskin; this species can weigh from 8 to 11.5 g. Among standard measurements, the wing chord is 5.5 to 7 cm, the tail is 3.9 to 4.7 cm, the bill is 0.9 to 1.1 cm and the tarsus is 1.1 to 1.2 cm. There is a slight NW-SE cline in size, with the largest birds from Mexico and south being up to one-fifth larger than the smallest from the extreme NW of its range.

There is considerable variation in the amount of black on head and back in males, thus three subspecies have been proposed. But this variation too seem to be simple and clinal changes in allele frequency, thus the "subspecies" might be better considered morphs or geographical forms. Males are recognized by their bright yellow underparts and big white patches in the tail and on the wings, they range from having solid black from the back to the upper head including the ear-coverts to having these regions medium green. In most of the range dark psaltria birds predominate; the light birds are termed hesperophilus and are most common in the far western U. S. and northwestern Mexico. The zone in which both light and dark males occur on a regular basis is broadest in the north, extends across the width of the Rocky Mountains and Sierra Madre Occidental ranges, it reaches the Pacific coast in southern Sonora to northern Sinaloa between area of Ciudad Obregón to Culiacán. In the United States, the most diverse array of phenotypes can be found in New Mexico.

East of the 106th meridian west in southwestern Texas as well as in most of Mexico all males have black backs. Spinus psaltria colombianus and south of the Isthmus of Tehuantepec, is richer yellow below in males; this as well as the yellower S. p. jouyi from the Yucatán Peninsula and adjacent regions and S. p. witti from the Islas Marías off Nayarit require more study as at least the former two seem to be larger and longer-billed. Females' and immatures' upperparts are less grayish olive-green, they have only a narrow strip of little or no white on the tail. They are best distinguished from other members of the genus by the combination of small size, upperparts without white or yellow, dark gray bill. In all plumages this bird can be taken for a New World warbler if the typical finch bill isn't seen well. Like other goldfinches, it has an undulating flight in which it gives a call: in this case, a harsh chig chig chig. Another distinctive call is a high-pitched, drawn-out whistle rising from one level pitch to another or falling.

The song is a prolonged warble or twitter, more phrased than that of the American goldfinch incorporating imitations of other species. This American goldfinch ranges from the southwestern United States to Peru, it migrates from the colder parts of its U. S. range. The lesser goldfinch occurs in flocks or at least loose associations, it utilizes any habitat with trees or shrubs except for dense forest, is common and conspicuous in many areas coming near houses. It is common at feeders in the Southwest United States and will come anywhere with thistle sock feeders. Flocks of at least six birds will be seen at feeders, it feeds on tree buds and weed seeds. The nesting season is in summer in the temperate parts of its range, it lays three or four bluish white eggs in a cup nest made of fine plant materials such as lichens and strips of bark, placed in a bush or at low or middle levels in a tree. The moult occurs in two different patterns which coincides with the blackness of the upperparts quite well.

Here too is a broad zone of intergradation. Pacific birds moult after breeding, females shed a few body feathers before breeding too. Juvenile males shed more remiges than females. East of the 106th meridian west, birds moult before breeding and replace another quantity of feathers afterwards, post-juvenal moult does not differ between the sexes. However, this seems dependent on the differing rainfall regimes. Considered a Species of Least Concern by the IUCN due to its vast range, it nonetheless se

Nekrasovskaya line

The Nekrasovskaya line is a metro line of the Moscow Metro. The first segment, between Kosino and Nekrasovka, was opened on 3 June 2019; the second segment is expected to open by the end of 2019 to 2020. City officials expect it to relieve passenger traffic on the Tagansko–Krasnopresnenskaya line once completed; the line will open together with a separate stretch of the Bolshaya Koltsevaya line from Nizhegorodskaya Ulitsa to Aviamotornaya, with through service between them. After the completion of the Bolshaya Koltsevaya line, service will be cut back to Nizhegorodskaya Ulitsa, with a cross-platform interchange to the other line. During construction, the line was referred to as the Kozhukhovskaya line. One concern about the name, which comes from a small village in the region, is that there is a Kozhukhovskaya station on the Lyublinsko–Dmitrovskaya line that got its name from a different village with the same name; therefore there was the possibility of confusion. The city opened a vote via its Active Citizen portal to rename the line to the Nekrasovskaya line.

The respondents voted in favor with 73.4% supporting the name change. As of November 2018, the official Moscow Metro map referred to the line as the Nekrasovskaya line; this marked the second time in two years that Moscow residents voted for a name change for a new transit line. In 2017, a similar vote resulted in a name change for the Bolshaya Koltsevaya line from its working name – Third Interchange Contour