Showing posts with label dictionary. Show all posts
Showing posts with label dictionary. Show all posts

Thursday, July 29, 2010

The purpose of steganography is to conceal the very presence of secret information.

剛剛收到的 空中英語教室電子報 200 期, 內容剛好是在討論 very 的形容詞用法, 內容如下:

The U.N.'s Law of the Sea Treaty aims to resolve this very question. (p. 50, line 2)

句中的 very 是形容詞、比較不常見的用法,它有「正是」的強調意味。

例句:

-- The topic you brought up is the very thing we discussed at our last meeting.

-- Barbara realized that her children had done the very thing she feared: they had all moved far from home.

在我的印象中, 我所讀的 steganography papers 中, 的確常常出現這樣的用法:

例如, 在 Jessica Fridrich 所寫的論文 "A New Steganographic Method for Palette-Based Images" 的 Introduction 中, 第二句就是這樣用的:
The purpose of steganography is to conceal the very presence of secret information.

From StegoRN

另外, 在 The Code Breakers 這本書中, Chapter 16 CENSORS, SCRAMBLERS, AND SPIES (P. 513) 中的第一段也有這樣的用法:
CIPHER IS THE LANGUAGE OF SPIES - and usually they must talk in whispers. A spy's success, his very existence, depends on his not being seen or heard. Sending messages in obviously cryptographic form would alert counterespionage to him as effectively as wearing a cloak and dagger. Yet he must transmit, else he is useless. So he eschews the overt methods of secret communications for the covert. He resorts to open codes, hollow heels, invisible inks, microscopically small missives - the steganographic methods that conceal the very fact that a message is being sent. He seeks to communicate unnoticed.

From StegoRN

最近在看的這本書 "Steganography in Digital Media" 中, 第 2 頁的第 2 段, 也是有相同的用法:
Note that the hidden message is unrelated to the content of the letter, which only serve as a decoy or "cover" to hide the very fact that a secret message is being sent. ...


如果你用 "to conceal the very existence" 當關鍵字在 Google 中搜尋, 相信也可以搜尋到許多 steganography 相關的論文或文章呢!

Wednesday, September 24, 2008

Bivariate Distribution & Marginal Distribution

Bivariate Distribution 顧名思義就是具有兩個隨機變數的分配。

From StegoRN

貓頭鷹出版社 所出版的 統計學辭典 中, 舉的例子非常容易理解: 特定構造與型示的二手車。一般來說, 對有興趣的買主來說, 二手汽車有兩個令人感興趣且容易測量的變數: 車齡 里程數

假設有一家二手車行購進了同一樣式的二手車 30 輛, 車行就可以將其依車子的使用年齡和行駛里程數製成一個二變量次數表。換句話說, 就是列出一個二維表格, 一維是車齡, 另一維是里程數, 表中統計符合條件的車輛數。例如: 使用 2-3 年, 行駛 4-5 萬英里的車子有 2 輛。在這個例子中, 兩個變數並不是相互獨立的, 較舊的車通常行駛較長的距離。

From StegoRN

如果表中所使用的是機率, 那就是一個 二變量機率分布 (bivariate probability distribution), 在二變量分配表上, 分別做行相加, 或列相加的動作, 所得出的分配就稱為 邊際分配 (marginal distribution)

在二手車的例子中, 邊際分配為:
里程數  0-10 10-20 20-30 30-40 40-50 50-60 60-70 70-80
車輛數  1   2   2   3   7   6   6   3

車 齡  0 - 1   1 - 2   2 - 3   3 - 4   4 - 5   5 - 6   6 - 7   7 - 8
車輛數  3   2   7   9   3   3   1   2

維基百科中的 聯合分布 ( joint probability distribution ) 條目的說明, 其實和這邊的 Bivariate Distribution 的解釋是差不多的, 指的應該就是同樣的東西。

Wednesday, March 19, 2008

The Difference between Conference and Workshop

昨天上課在討論時, 研究生問我 conference 和 workshop 有什麼不同? 我記得前幾個禮拜曾經在空中英語教室 chatroom 聽過這麼一段討論, 於是就把檔案找出來一起聽聽看。剛剛想到和黃世育老師規劃非資訊學院科系大二多媒體課程時, 有納入音訊檔的簡單處理, 黃老師建議使用 GoldWave , 於是就上網搜尋這個軟體下載, 想要把 chatroom 這一段單獨剪輯成一個檔案, 放在這邊給研究生分享。


Friday, December 01, 2006

Steganography in Merrian-Webster Online

前幾天收到 Merrian-Webster Online 用 email 寄來的 Word of the Day ( November 26, 2006 ) 剛好就是介紹 steganography 這個字, 這個字之前我在 Merrian-Webster Online 是查不到的, 不過現在已經補上來了, 我們來看看 email 的介紹內容:
steganography \steg-uh-NAH-gruh-fee\ noun

: the art or practice of concealing a message, image, or file within another message, image, or file

Example sentence:
No doubt, the Internet has enriched society, but it has a flip side; terrorists, for instance, can secretly network online using steganography.

Did you know?
"Steganography" is a word that was resurrected after being in disuse for almost 150 years! It was put to rest in the early 1800s, labeled an archaic synonym of "cryptography" by dictionary makers, but was brought back to life in the 1980s as a word for a type of digital cryptography. There is nothing cryptic about the word's origin; it is based on the Greek word "steganos," meaning "covered" or "reticent."
steganography 在 Merrian-Webster Online 的連結網址是 http://www.m-w.com/dictionary/steganography
我們也來看看它是怎麼介紹的:
Main Entry: steg·a·nog·ra·phy
Pronunciation: "ste-g&-'nä-gr&-fE
Function: noun
Etymology: New Latin steganographia, from Greek steganos covered, reticent (from stegein to cover) + Latin -graphia -graphy -- more at THATCH
1 archaic : CRYPTOGRAPHY
2 : the art or practice of concealing a message, image, or file within another message, image, or file
- steg·a·no·graph·ic /-n&-'gra-fik/ adjective
相對於 cryptography 的 steganography, Merrian-Webster Online 已經有解釋了, 不過, 相對於cryptanalysis 的 steganalysis, 不曉得還要等多久, 字典的解釋才會補上來...