Week 02: Information Hiding

1. 課本圖 1.1 秘密通訊的流程的原始來源是 Information Hiding - A survey [ PDF ] 的 Fig. 1. A classification of information hiding techniques.



2. Enigma



3. Bletchley Park

　
　
　

Week 01: 本課程評分規則

1. 98學年度上學期本課程評分標準

　a. 小考二次 (20% + 20%)
　b. 故事書三選一閱讀分享 (20%)
　c. 論文閱讀一篇 (20%)
　d. 學習態度: 出缺席, 課堂睡覺, 互動討論參與 (20%)
　e. 程式撰寫 (20%)

2. 教科書: 資訊媒體安全 - 偽裝學與數位浮水印

　　

　定價: 560 元, 團購價: 420 元。
　可於 9/24 課堂上繳費領書。

3. 故事書:

　　　　

4. 作業繳交部落格 Homework Show @ IHC

　請修課同學在本篇文章中, 留下學號與 email , 我會發共同作者的邀請信給你, 讓你有權限可以在作業部落格繳交作業。

News: Gordon Brown: I'm proud to say sorry to a real war hero

Gordon Brown: I'm proud to say sorry to a real war hero
The treatment of code-breaker Alan Turing was utterly unfair, says Gordon Brown

By Gordon Brown
Published: 9:30PM BST 10 Sep 2009
Original Link

This has been a year of deep reflection – a chance for Britain, as a nation, to commemorate the profound debts we owe to those who came before. A unique combination of anniversaries and events have stirred in us that sense of pride and gratitude that characterise the British experience. Earlier this year, I stood with Presidents Sarkozy and Obama to honour the service and the sacrifice of the heroes who stormed the beaches of Normandy 65 years ago. And just last week, we marked the 70 years which have passed since the British government declared its willingness to take up arms against fascism and declared the outbreak of the Second World War.

So I am both pleased and proud that, thanks to a coalition of computer scientists, historians and LGBT (lesbian, gay, bisexual and transgender) activists, we have this year a chance to mark and celebrate another contribution to Britain's fight against the darkness of dictatorship: that of code-breaker Alan Turing.


Computer pioneer Alan Turing, who helped crack German Enigma codes during WWII

Turing was a quite brilliant mathematician, most famous for his work on breaking the German Enigma codes. It is no exaggeration to say that, without his outstanding contribution, the history of the Second World War could have been very different. He truly was one of those individuals we can point to whose unique contribution helped to turn the tide of war. The debt of gratitude he is owed makes it all the more horrifying, therefore, that he was treated so inhumanely.

In 1952, he was convicted of "gross indecency" – in effect, tried for being gay. His sentence – and he was faced with the miserable choice of this or prison – was chemical castration by a series of injections of female hormones. He took his own life just two years later.

Thousands of people have come together to demand justice for Alan Turing and recognition of the appalling way he was treated. While Turing was dealt with under the law of the time, and we can't put the clock back, his treatment was of course utterly unfair, and I am pleased to have the chance to say how deeply sorry I and we all are for what happened to him. Alan and the many thousands of other gay men who were convicted, as he was convicted, under homophobic laws, were treated terribly. Over the years, millions more lived in fear in conviction. I am proud that those days are gone and that in the past 12 years this Government has done so much to make life fairer and more equal for our LGBT community. This recognition of Alan's status as one of Britain's most famous victims of homophobia is another step towards equality, and long overdue.

But even more than that, Alan deserves recognition for his contribution to humankind. For those of us born after 1945, into a Europe which is united, democratic and at peace, it is hard to imagine that our continent was once the theatre of mankind's darkest hour. It is difficult to believe that in living memory, people could become so consumed by hate – by anti-Semitism, by homophobia, by xenophobia and other murderous prejudices – that the gas chambers and crematoria became a piece of the European landscape as surely as the galleries and universities and concert halls which had marked out the European civilisation for hundreds of years.

It is thanks to men and women who were totally committed to fighting fascism, people like Alan Turing, that the horrors of the Holocaust and of total war are part of Europe's history and not Europe's present. So on behalf of the British government, and all those who live freely thanks to Alan's work, I am very proud to say: we're sorry. You deserved so much better.

YouTube: How NOT To Use Powerpoint By Comedian Don McMillan

Week 17: JPEG Compression & Steganography

今天是最後一次上課, 課程主題分成三個部份:

1. JPEG Compression

我們示範了 JPEG 壓縮的整個過程, 並以一個 Block 為例子,
a. 將原先的 RGB 色彩值轉換成 YCbCr 值,
b. 再分別轉換成 DCT 係數,
c. 使用一個量化參數(quantization factor) 來設定量化表 (quantization table),
d. 對 DCT 係數矩陣做量化處理
e. 將量化後係數 (quantized coefficients) 轉成一維的 Zigzag 序列。

2. JPEG Steganography

討論在JPEG壓縮過程中, 如何嵌入資訊, 並以 Jsteg 為例子。

3. 課程成效檢討

Week 16: JPEG Compression (2)

今天上午我要參加兒子的國小畢業典禮, 所以課程由黃老師代課。請大家延續上週的討論, 繼續探索 JPEG 壓縮標準。

請大家繼續思索的問題是:
1. 針對每一個經 DCT 轉換後所得到的 8*8 係數矩陣, 都要使用一個同樣是 8*8 大小的量化矩陣做量化壓縮程序。為什麼量化矩陣中, 不同位置的值大小不同, 代表的涵義為何?
2. 量化後的係數矩陣中, 存在許多個 0, 代表的涵義為何?
3. 用 Zigzag 的方式, 將二維矩陣轉換為一維矩陣的目的為何? 優點為何?
4. 為什麼 JPEG 壓縮的最後一個步驟必須使用無失真的壓縮技術?
5. 熵編碼(entropy coding)的熵所代表的意義為何?

同學們了解了整個 JPEG 壓縮過程後, 就可以自行思索如果想嵌入機密訊息到 JPEG 影像中, 可以放到哪個位置之中。

下星期請大家繳交一篇學期課程回顧與心得, 然後給自己打一個分數, 分享到 Homework Show @ IHC 中, 請同學務必繳交並出席下週的課程。
　

Week 15: JPEG Compression (1)

本週的討論主題為 JPEG Compression。
我們先請同學閱讀在中文維基百科中 JPEG 條目, 然後就同學提出的問題討論。

討論的內容包含:
1. 什麼是色彩空間? 為什麼有不同的色彩空間? 轉換的目的為何?
2. 什麼是量化? 好處是什麼?
3. 什麼是轉換? 為什麼要做 DCT 轉換?
4. DCT 轉換後的矩陣的意義為何? 何謂低頻? 何謂高頻? 對應到一張影像所呈現的意義是什麼?

這些都是同學應該思考的核心觀念, 觀念貫通了, 技術與程式就不會是問題! 請同學就上述問題, 多方搜尋資料, 解答自己的困惑, 整理自己的想法, 分享到 Homework Show @ IHC 中。