explain xkcd - User contributions [en]

3054: Scream Cipher

2025-02-22T01:28:02Z

172.70.47.112: /* Table */ Connections between symbols and letters

{{comic
| number = 3054
| date = February 21, 2025
| title = Scream Cipher
| image = scream_cipher_2x.png
| imagesize = 287x416px
| noexpand = true
| titletext = AAAAAA A ÃA̧AȂA̦ ǍÅÂÃĀÁȂ AAAAAAA!
}}

==Explanation==
{{incomplete|Created by A ÃA̧ȂÁAǍẢÂA̋ ȦÅĀ - Please change this comment when editing this page. Do NOT delete this tag too soon.}}
A {{w|Cipher}} is a method of encryption, where characters or sometimes words are substituted for other characters in a set pattern, allowing for arbitrary strings to be enciphered using it. The complexity and strength of ciphers varies, from {{w|one-time pads}} and (historically) {{w|enigma machine|Enigma}} as stronger and more complex, to {{w|substitution ciphers}} as some of the weakest and least complex, where each character is simply given a set different symbol to represent it in the cipher.

This comic uses a substitution cipher, where all the letters of the English Alphabet are represented using the letter "A", with different {{w|diacritical marks}} to define the differences. This kind of cipher is often used on a recreational basis by children or casual enthusiasts, the similarity of the letters increasing the obcurity of the content and the skill or technology required for use, but there is also significant impracticality, as not only are substitution ciphers the easiest to break, but also the similarities in the letters do make the cipher hard to read and easy to misread, and the detail in the diacritical marks makes it easy to draw the "A"s incorrectly or ambiguously, potentially leading to [[3003: Sandwich Helix|part of the message being lost]]. This was our experience in the comments section of this very article, where one person implemented translator functions alongside another person crafting a message that failed to translate. However, the logic behind the code is mostly visual similarity, and if attentive to connecting concepts between the American and scream cipher alphabet, it could be quickly learned and translated in a glance.

It's named "Scream Cipher" (as a pun on {{w|stream cipher}}s, commonly used in computing) because the written form of a scream is a long string of As, possibly with some other characters at the end (and often an exclamation point for emphasis), such as "Aaaaaah!" or "Aaaaaaagh!". The name may or may not be a reference to IBM's {{w|Scream_(cipher)|Scream cipher}} published in 2002.

In the comic, [[Cueball]] texts the ciphered version for the plaintext "HELLO", and [[Megan]] responds with that for "HI".

The title text deciphers to "AAAAAA A SCARY MONSTER AAAAAA!"

You can translate text to and from Scream Cipher using [https://github.com/matthewpwatkins/scream-cipher/ the Scream Cipher Translator].

Another recent comic featuring all "A"s was [[2957: A Crossword Puzzle]].

==Worked example==



Say we want to encode "Scream" in the Scream Cipher. First we would need to split out word into the letters, so S, C, R, E, A, M.

The first letter is S, so if we go to S in the table S is shown to become to Ã, C similarly becomes A̧, R becomes Ȃ, E corresponds to Á, A is the main letter so A is unchanged to A, and M becomes Ǎ. If we then write them again in order, we find SCREAM becomes ÃA̧ȂÁAǍ.

To turn cipher text back into normal text, the process is repeated in reverse. To translate A̧ẢA̯A̰ÁȂ, we go to A̧ in the table and find A̧ becomes C. Ả similarly becomes I, A̯ becomes P, A̰ becomes H, Á becomes E, and Ȃ becomes R. If we write the letters in order, we see that A̧ẢA̯A̰ÁȂ becomes CIPHER.

The symmetry of subtitution ciphers is apparent in the example, as in the SCREAM example R becomes Ȃ and E becomes Ȃ, and in the CIPHER example in the opposite direction Ȃ goes back to being R, and Ȃ goes back to being E, though in a different order.

==Table==

The {{w|Unicode}} names of the characters in the cipher are as follows:

{|class="wikitable"
! colspan=2 | Input !! colspan=3 | Substitution
|-
! Plain !! Unicode description !! Cipher !! Unicode description(s) !! Usage note
|-
| A || U+0041 LATIN CAPITAL LETTER A || A || '''U+0041 LATIN CAPITAL LETTER A || Unadorned base character
|-
| B || U+0042 LATIN CAPITAL LETTER B || Ȧ || '''U+0226 LATIN CAPITAL LETTER A WITH DOT ABOVE ||
|-
| C || U+0043 LATIN CAPITAL LETTER C || A̧ || U+0041 LATIN CAPITAL LETTER A, '''U+0327 COMBINING CEDILLA''' ||
|-
| D || U+0044 LATIN CAPITAL LETTER D || A̱ || U+0041 LATIN CAPITAL LETTER A, '''U+0331 COMBINING MACRON BELOW''' ||
|-
| E || U+0045 LATIN CAPITAL LETTER E || Á || '''U+00C1 LATIN CAPITAL LETTER A WITH ACUTE || Many words have an acute e, as in "fiancé".
|-
| F || U+0046 LATIN CAPITAL LETTER F || A̮ || U+0041 LATIN CAPITAL LETTER A, '''U+032E COMBINING BREVE BELOW''' ||
|-
| G || U+0047 LATIN CAPITAL LETTER G || A̋ || U+0041 LATIN CAPITAL LETTER A, '''U+030B COMBINING DOUBLE ACUTE ACCENT''' ||
|-
| H || U+0048 LATIN CAPITAL LETTER H || A̰ || U+0041 LATIN CAPITAL LETTER A, '''U+0330 COMBINING TILDE BELOW''' ||
|-
| I || U+0049 LATIN CAPITAL LETTER I || Ả || '''U+1EA2 LATIN CAPITAL LETTER A WITH HOOK ABOVE ||
|-
| J || U+004A LATIN CAPITAL LETTER J || A̓ || U+0041 LATIN CAPITAL LETTER A, '''U+0313 COMBINING COMMA ABOVE''' ||
|-
| K || U+004B LATIN CAPITAL LETTER K || Ạ || '''U+1EA0 LATIN CAPITAL LETTER A WITH DOT BELOW ||
|-
| L || U+004C LATIN CAPITAL LETTER L || Ă || '''U+0102 LATIN CAPITAL LETTER A WITH BREVE ||
|-
| M || U+004D LATIN CAPITAL LETTER M || Ǎ || '''U+01CD LATIN CAPITAL LETTER A WITH CARON ||
|-
| N || U+004E LATIN CAPITAL LETTER N || Â || '''U+00C2 LATIN CAPITAL LETTER A WITH CIRCUMFLEX ||
|-
| O || U+004F LATIN CAPITAL LETTER O || Å || '''U+00C5 LATIN CAPITAL LETTER A WITH RING ABOVE || The symbol contains the letter 'O'.
|-
| P || U+0050 LATIN CAPITAL LETTER P || A̯ || U+0041 LATIN CAPITAL LETTER A, '''U+032F COMBINING INVERTED BREVE BELOW''' ||
|-
| Q || U+0051 LATIN CAPITAL LETTER Q || A̤ || U+0041 LATIN CAPITAL LETTER A, '''U+0324 COMBINING DIAERESIS BELOW''' ||
|-
| R || U+0052 LATIN CAPITAL LETTER R || Ȃ || '''U+0202 LATIN CAPITAL LETTER A WITH INVERTED BREVE ||
|-
| S || U+0053 LATIN CAPITAL LETTER S || Ã || '''U+00C3 LATIN CAPITAL LETTER A WITH TILDE ||
|-
| T || U+0054 LATIN CAPITAL LETTER T || Ā || '''U+0100 LATIN CAPITAL LETTER A WITH MACRON ||
|-
| U || U+0055 LATIN CAPITAL LETTER U || Ä || '''U+00C4 LATIN CAPITAL LETTER A WITH DIAERESIS || Many German words have a 'ü', as in "[[w|Fahrvergnügen]]"
|-
| V || U+0056 LATIN CAPITAL LETTER V || À || '''U+00C0 LATIN CAPITAL LETTER A WITH GRAVE ||
|-
| W || U+0057 LATIN CAPITAL LETTER W || Ȁ || '''U+0200 LATIN CAPITAL LETTER A WITH DOUBLE GRAVE ||
|-
| X || U+0058 LATIN CAPITAL LETTER X || A̽ || U+0041 LATIN CAPITAL LETTER A, '''U+033D COMBINING X ABOVE''' ||
|-
| Y || U+0059 LATIN CAPITAL LETTER Y || A̦ || U+0041 LATIN CAPITAL LETTER A, '''U+0326 COMBINING COMMA BELOW''' ||
|-
| Z || U+005A LATIN CAPITAL LETTER Z || Ⱥ || '''U+023A LATIN CAPITAL LETTER A WITH STROKE ||
|}

==Transcript==
{{incomplete transcript|Do NOT delete this tag too soon.}}

:[Top of the panel has 26 letters of the alphabet, each followed by a hyphen and the letter "A" with a unique diacritical mark for each. "A - A" at the top is an exception, where the latter doesn't have a diacritic.]
:{|
|A - A
|-
|B - Ȧ
|G - A̋
|L - Ă
|Q - A̤
|V - À
|-
|C - A̧
|H - A̰
|M - Ǎ
|R - Ȃ
|W - Ȁ
|-
|D - A̱
|I - Ả
|N - Â
|S - Ã
|X - A̽
|-
|E - Á
|J - A̓
|O - Å
|T - Ā
|Y - A̦
|-
|F - A̮
|K - Ạ
|P - A̯
|U - Ä
|Z - Ⱥ
|}
:[Cueball and Megan typing on their phones, Cueball with two hands and Megan with one hand.]
:Cueball's phone: A̰ÁĂĂÅ
:Megan's phone: A̰Ả

:[Caption below the panel:]
:In the ''Scream Cipher'', messages consist of all As, with different letters distinguished using diacritics.

{{comic discussion}}

[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Language]]
[[Category:Cryptography]]
[[Category:Unicode]]

Talk:394: Kilobyte

2025-01-06T12:04:59Z

172.70.47.112: Added trivia about the N64's RAM.

The drivemaker's version here does 'depreciate' their kilobyte, indeed, but rather than based on slipping food-standards (which are often highly regulated) I think this is actually based upon the actual age-old practice of them sometimes using 10<sup>3n</sup> (1,000s, 1,000,000s, etc) measures of byte-multiplies in preference to 2<sup>10n</sup> ones (1,024, 1,048,576, etc) in order to get a better figure. For example 20MB drives (back in the old days, this is) with 971,520 bytes (almost 1Mb, by either measure) ''less'' than the true binary-matching 20MiB value which various computer OSes would work with. (Or a 'binarily' 20MB drive gets advertised as "20.1MB" one.) On the other hand, something that "needs 20Mb of installation space" might have deliberately been given the binary-divisible version of the unit to make it look marginally less resource-hungry than the decimalised measure would have indicated. Minor differences in their own right, on a bad day when the competing standards mesh badly you might find yourself just short of storage space when you thought you'd be Ok.

Although in real-life the difference between any given unit's interpretation has ''not'' changed, as equipment capacities increases and we start to use increasing degrees of prefix upwards, any discrepancy becomes more significant. 1KB is plus or minus 24 bytes (~2%), 1MB is plus or minus around 48KB (~5%), 1GB is plus or minus 73MB (~7%) and 1TB could be very nearly 100Gb short (~10%). For those that care about these things that's at the very least annoying. Like with CRT monitor sizes that were often more an indicator of tube-end size than the true size of the visible/illuminatable portion, giving them an inch or two less of effective display than you might expect. [[Special:Contributions/178.98.31.27|178.98.31.27]] 13:55, 18 June 2013 (UTC)

:Just to follow-up to myself, based upon a unit capitalisation discrepancy that I only spotted post-posting, but that I won't bother fixing, there's also the old confusion between "kilobits-per-second" and "kilo''bytes''-per-second" (and mega- and giga- versions, more recently with broadband and more advanced ethernets/etc) when it comes to bandwidths and expected speeds. Although you don't necessarily expect to exactly hit the stated limit (with contentions and collisions and latencies and overheads), getting a factor of 8 less than you might have expected has caught people out before, thinking they're getting a far poorer service than advertised... (Not that this has much to do with the above comic, just saying. And, oh lookie here on my desk. A 28,800 'Sportster' PCMCIA faxmodem card (V34, V32bis) with an XJACK® pop-out socket. Why have I still got that?) [[Special:Contributions/178.98.31.27|178.98.31.27]] 14:16, 18 June 2013 (UTC)

This table fails to mention, of course, that while a Baker's Kilobyte is 1152 bytes normally, it's 1125 on leap years. [[User:Hppavilion1|Hppavilion1]] ([[User talk:Hppavilion1|talk]]) 23:21, 26 October 2017 (UTC)

Apparently, the N64 has 4.5 MBa of RAM. Learned this from a Kaze Emanuar video recently. I'm at work, so can't look up the video now, otherwise I'd link it. [[Special:Contributions/172.70.47.112|172.70.47.112]] 12:04, 6 January 2025 (UTC)

== What is the source of the "official" definition of the kilobyte? ==

From the article at time of creating this topic: "the official definition now states that 1 kilobyte is 1000 bytes". This is official according to whom exactly? I may have missed a citation somewhere but I think this clause needs a citation in the text of the the article. AzureArmageddon 13:50, 3 October 2023 (UTC)
:Well, SI and IEC either state or 'recommend' that a kilobyte (kB) is 10³ bytes, while tradition has tended to use KB (capital-K) for 2¹⁰ bytes (obviously open for confusion) while IEC defines this as a 'kibibyte' (KiB). There's several possible cites for that, one really would need to decide which look best/official.
:As a general hint to people, though, I think that makes it probably best to just always use explicit KiBs, and mibi/gibi/tebi/etc equivalents, in full or as unit abbreviations, because there might be people who haven't got the memo/don't know whether ''you'' got the memo, otherwise. And at least there's a chance that even those unaware of "FOObibytes" will try to find out what these are... unless they just mistake them for typos or read them unconsciously wrongly, but then there's probably more problems than just assuming the wrong base-multiple... ;) [[Special:Contributions/172.70.86.54|172.70.86.54]] 17:26, 3 October 2023 (UTC)
::I agree with you on that best practice for sure. I don't feel qualified to determine which authority is most authoritative, though. Hoping someone with relevant industry credentials can make a qualified opinion. AzureArmageddon 15:56, 5 October 2023 (UTC)