[原创]Reflections on talk by Prof PK Lam

发布者: ccfeng | 发布时间: 2006-7-18 22:55| 查看数: 11625| 评论数: 3|帖子模式

Last Tuesday, I attended a talk by the world renowned Photonics expert from <place wst="on"></place><place></place><place></place><place></place><place></place><place></place><place></place><place></place><placename wst="on"></placename><placename></placename><placename></placename><placename></placename><placename></placename><placename></placename><placename></placename><placename></placename>Australian<placename></placename><placename></placename><placename></placename><placename></placename><placename></placename><placename></placename><placename></placename><placename></placename> <placename wst="on"></placename><placename></placename><placename></placename><placename></placename><placename></placename><placename></placename><placename></placename><placename></placename>National<placename></placename><placename></placename><placename></placename><placename></placename><placename></placename><placename></placename><placename></placename><placename></placename> <placetype wst="on"></placetype><placetype></placetype><placetype></placetype><placetype></placetype><placetype></placetype><placetype></placetype><placetype></placetype><placetype></placetype>University<placetype></placetype><placetype></placetype><placetype></placetype><placetype></placetype><placetype></placetype><placetype></placetype><placetype></placetype><placetype></placetype><place></place><place></place><place></place><place></place><place></place><place></place><place></place><place></place>, Prof PK Lam. The Topic is: Usual Common Optics to Build the Ultimate Cryptography System?Overall, it was about the war between the code-makers and code-breakers and the usage of quantum mechanics to create an unbreakable code. With high level of physics involved, the talk was kept simple and few science terms were used.

rofessor Lam started with a quote from a famous cryptographer which said that all codes could be deciphered in one way or another. Firstly, he simply went through the History of Cryptography, to make us understand the background of cryptography more so we could comprehend the difficult quantum mechanics part. The first topic he touched on was the art of cryptography, it was a really simple. Despite being simple, it was truly fascinating and captured our attention. The examples Prof Lam provided were: Greek wax tables, tattoos on slaves shaved heads, swallowing of waxed silk scarves, jumping alphabet, micro-dot, invisible ink and digital information hiding. I was most surprised by the examples, tattoos on slaves shaved heads and swallowing of waxed silk scarves. Tattoos on a person’s head? It was really weird to write codes on a person’s head! Prof Lam also disapproved this method as it was too troublesome and the code would get decrypted easily. However, it was still an interesting art of cryptography people came up with. How about swallowing of waxed silk scarves? After hearing Prof Lam’s explanation, the audience emitted sounds of disgust. It was just simply wrapping up the secret message with silk scarves, dip it in wax and swallow it! Not easy to dig up messages from ones stomach eh?Next, Prof Lam enlightened us about the silent struggle between the code-maker and code-breaker. The code-maker struggled to get the encrypted message forward to the code-receiver without being deciphered by the code-breaker. In the meantime, the code-breaker struggled to capture the code and decrypt the code to get the information. Thus, we could see that a “war” was really going on between the code-makers and code-breakers.

rof Lam also lectured on Classical Cryptography, Medieval Cryptography WWII Cryptography and Modern Cryptography. Dating from 4500BC to present time, it showed us the rich history of cryptography and the way the methods of cryptography progressed with time. Starting from Classical Cryptography which dated from 4500BC-500AD, Prof Lam presented to us the origins of cryptography and it amazed us that encryption started as early as 4500BC. Although too simple to us, it was great to know that cryptography had such a long history. Why encrypt the information? Prof Lam explained the reasons and motivations behind encryption such as politically, economically or socially motivated.Another interesting topic was World War II Cryptography. Although there was no big difference compared earlier cryptographic schemes, the complexity was greatly increased. There was the Enigma Code used by <country-region wst="on"></country-region><country-region></country-region><country-region></country-region><country-region></country-region><country-region></country-region><country-region></country-region><country-region></country-region><country-region></country-region><place wst="on"></place><place></place><place></place><place></place><place></place><place></place><place></place><place></place>Germany<place></place><place></place><place></place><place></place><place></place><place></place><place></place><place></place><country-region></country-region><country-region></country-region><country-region></country-region><country-region></country-region><country-region></country-region><country-region></country-region><country-region></country-region><country-region></country-region> which was eventually broken by the English; the Purple Code used by the Japanese, broken too; and the Navajo Code Talker used by the Americans which was never broken by the enemy. Why the Navajo Code Talker was never broken? It was really interesting. The Navajos were the Native Americans and the truth was, the Navajo Code Talker was just a native language spoken between the Navajos, so nobody understood them! Therefore, the “code” was never deciphered by enemies.Modern Cryptography, mainly economically motivated. People in modern times wanted to keep their personal information silent so their information was encrypted. There were also banks, online information, credit card information and so much that people wanted to keep secret in this complicated world. The cryptographic system would be much more complicated in order to protect our information. A new chapter of cryptography history was started as more and more methods emerged.Now came the difficult quantum mechanics part, it was really hard to understand everything in this 1-hour talk. I had not learnt the complicated physics behind the cryptographic scheme but with Professor Lam’s good explanation, I was able to capture the main idea of the whole thing. How to create an unbreakable code? As Prof Lam went through, I understood that the code-breaker was always around, all-knowing and had a perfect system to decode. Thus, the code-makers need a good system to protect the information from the code-breaker.How to achieve the ultimate goal of an unbreakable code? It was by randomness. It was difficult for man to achieve total randomness and computers also could not, but it was easy for Physics. For example, light was shone on a piece of glass which reflects light with a possibility of 50%, thus total randomness was achieved as it was a 50-50 chance for light to reflect or pass through. This was when quantum mechanics came in to bring forward total randomness for an unbreakable code.One example brought forward by Prof Lam was the One Time Pad, which was deemed unbreakable. However, it was still not the best, perfect system as the code-maker must use a new keyboard each time to be safe. Imagine having to change a keyboard everyday! Certainly not a neat idea.Good methods suggested by Prof Lam were: Laser beam, laser noise, scatter diagrams and the Mastermind Game. As we could see, laser was really useful not only in other fields, but also in the field of cryptography. For those who had played the Mastermind Game, which was in fact a game, would understand what it was all about.However, the best suggested method for an unbreakable code would be Privacy Amplification. Although the concepts in physic terms were complicated, Prof Lam explained in really very simple terms and all of us could understand easily. To put it in simple words, the code-maker wanted to send an image to the receiver, but the code-breaker would always capture the image with the aid of a good system. In order to make the code-breaker get nothing at all, the code-maker would make use of quantum mechanics to give the receiver a perfect image while let the code-breaker get a little flawed image. How to make the code-breaker get a totally blurred image? In simple terms, it was to manipulate the flaw with Privacy Amplification in the code-breaker’s image and make the flaw spread over the entire image. It was just like kneading dough. For example, the dough had a patch of ink on it, in order to make the whole dough covered with ink, the person just need to knead and knead the dough until the ink spread. By doing so, the code-breaker’s data would be contaminated and would get an image with totally nothing at all.

rof Lam ended his talk saying that, “It can be squarely asserted that quantum physics can generate a cipher key which is absolutely unbreakable.” Thus, Prof Lam was suggesting that it was totally possible to create an unbreakable code with the help of quantum physics.In conclusion, I think this is really an enriching talk as we are given up-to-date information about cryptography. It is a rare chance too for an external speaker to put the ideas of cryptography forward simply without all the complicated science terms. Cryptography is really a fascinating topic to study about and it is never ending as new better methods of code-making and code-breaking emerged one after the other. My motivation to attend this talk is because of the movie “The Da Vinci Code” as this movie had increased my interest in cryptography. This marvelous talk has given me good information and I have a better understanding of cryptography now.

[此贴子已经被作者于2006-7-18 23:57:30编辑过]

Lam, Photonics, Prof, Reflections, talk

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ccfeng 发表于 2006-7-18 23:05:09

How to break secret codes? From: HON CHIEW WENG <pre>Dear Students, Those who are amused by Da Vinci Code may wish to find out more about the silent war between code-makers and code-breakers. You may wish to note that quantum mechanics can be used by code-makers to build an unbreakable cryptographic system. We are pleased to inform that the world renowned Photonics expert from Australian National University,Prof PK Lam will be in Singapore. next week. We managed to invite him to give a short talk on 11 July (Tue) at LT2 (High School section) at 3 pm. Topic of the talk: Usual Common Optics to Build the Ultimate Cryptography System? In this talk, Prof Lam will discuss in simple non-mathematical terms (so that non-science students can also understand) what it takes to use Quantum Mechanics for cryptographic communication.   If yu are interested to attend, pls click "A" so that we could reserve a seat for you. After the talk, you may write a reflection and submit to your science teachers for ACE points. See you there. Hon </pre>

[此贴子已经被作者于2006-7-19 19:27:36编辑过]

yangye602 发表于 2006-7-20 11:01:19

Thanks to your explanation, I have also caught up the complex theory more or less. I really appreciate you for bringing such a charming article!~~

puppy 发表于 2006-7-22 10:49:09

Dear CCfeng,<span lang="EN-US" style="FONT-SIZE: 10.5pt; FONT-FAMILY: "Times New Roman"; mso-fareast-font-family: 宋体; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-bidi-font-size: 12.0pt;">    Thanks for your detailed minutes of cryptography given by Prof Lam, it serves a window of the long and interesting history of cryptography from the period BC till now.  Just as you said, the marvelous technology of cryptography will never be obsolete as the countless methods between encryption and decryption is mutually competent and complementary so as to maintain its cutting edge in modern science.  As to the technology term quantum mechanics I don't know much about it.  But the unbreakable encryption used with Navajo that keep the deliberate code breaker away from knowing the details about the important military information in WWII is really interesting.  It reminds me of another film Alien vs predator, some mysterious encryption techniques were also applied in that horrible and cryptic pyramid.  Some scientists and experts went to great length to dig up that building and eventually figure the problem.  That film is one of the best favorites I ever seen for entertainment and the interesting fighter between the decryption and the encryption so that it’s strongly recommended that you take a look at it.<span lang="EN-US" style="FONT-SIZE: 10.5pt; FONT-FAMILY: "Times New Roman"; mso-fareast-font-family: 宋体; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-bidi-font-size: 12.0pt;">

[此贴子已经被作者于2006-7-22 10:50:41编辑过]

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[原创]Reflections on talk by Prof PK Lam

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