Is Bitcoin Anonymous? Arvind Narayanan | Princeton University | Real World Cryptography Workshop
Arvind Narayanan | Princeton University Is Bitcoin Anonymous? January 13th, 2014 Real World Cryptography Workshop: Hi-Def. Monday, January 13 Session 1: Bitc...
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Is Bitcoin Anonymous? Arvind Narayanan | Princeton University | Real World Cryptography Workshop - Video
Public Key Cryptography: RSA Encryption Algorithm
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Public Key Cryptography: RSA Encryption Algorithm - Video
Cryptography: Secret Coding, Spying, and E-Commerce
Edward Felten, professor of computer science and public affairs and director of the Center for Information Technology Policy, discusses "Cryptography: Secret...
By: Princeton Engineering Lectures
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Cryptography: Secret Coding, Spying, and E-Commerce - Video
As a graduate student at the Massachusetts Institute of Technology in 1996, Amit Sahai was fascinated by the strange notion of a zero-knowledge proof, a type of mathematical protocol for convincing someone that something is true without revealing any details of why it is true. As Sahai mulled over this counterintuitive concept, it led him to consider an even more daring notion: What if it were possible to mask the inner workings not just of a proof, but of a computer program, so that people could use the program without being able to figure out how it worked?
The idea of obfuscating a program had been around for decades, but no one had ever developed a rigorous mathematical framework for the concept, let alone created an unassailable obfuscation scheme. Over the years, commercial software companies have engineered various techniques for garbling a computer program so that it will be harder to understand while still performing the same function. But hackers have defeated every attempt. At best, these commercial obfuscators offer a speed bump, said Sahai, now a computer science professor at the University of California, Los Angeles. An attacker might need a few days to unlock the secrets hidden in your software, instead of a few minutes.
Secure program obfuscation would be useful for many applications, such as protecting software patches, obscuring the workings of the chips that read encrypted DVDs, or encrypting the software controlling military drones. More futuristically, it would allow people to create autonomous virtual agents that they could send out into the computing cloud to act on their behalf. If, for example, you were heading to a remote cabin in the woods for a vacation, you could create and then obfuscate a computer program that would inform your boss about emails you received from an important client, or alert your sister if your bank balance dropped too low. Your passwords and other secrets inside the program would be safe.
You could send that agent into the computing wild, including onto untrusted computers, Sahai said. It could be captured by the enemy, interrogated, and disassembled, but it couldnt be forced to reveal your secrets.
As Sahai pondered program obfuscation, however, he and several colleagues quickly realized that its potential far surpassed any specific applications. If a program obfuscator could be created, it could solve many of the problems that have driven cryptography for the past 40 years problems about how to conduct secure interactions with people at, say, the other end of an Internet connection, whom you may not know or trust.
A program obfuscator would be a powerful tool for finding plausible constructions for just about any cryptographic task you could conceive of, said Yuval Ishai, of the Technion in Haifa, Israel.
Precisely because of obfuscations power, many computer scientists, including Sahai and his colleagues, thought it was impossible. We were convinced it was too powerful to exist, he said. Their earliest research findings seemed to confirm this, showing that the most natural form of obfuscation is indeed impossible to achieve for all programs.
Then, on July 20, 2013, Sahai and five co-authors posted a paper on the Cryptology ePrint Archive demonstrating a candidate protocol for a kind of obfuscation known as indistinguishability obfuscation. Two days later, Sahai and one of his co-authors, Brent Waters, of the University of Texas, Austin, posted a second paper that suggested, together with the first paper, that this somewhat arcane form of obfuscation may possess much of the power cryptographers have dreamed of.
This is the first serious positive result when it comes to trying to find a universal obfuscator, said Boaz Barak, of Microsoft Research in Cambridge, Mass. The cryptography community is very excited. In the six months since the original paper was posted, more papers have appeared on the ePrint archive with obfuscation in the title than in the previous 17 years.
However, the new obfuscation scheme is far from ready for commercial applications. The technique turns short, simple programs into giant, unwieldy albatrosses. And the schemes security rests on a new mathematical approach that has not yet been thoroughly vetted by the cryptography community. It has, however, already withstood the first attempts to break it.
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Cryptography Breakthrough Could Make Software Unhackable ...
1. List some of the attacks on the Diffie-Hellman key exchange protocol we discussed in the lecture. Present your solution for avoiding such attacks. 2. In the Diffie-Helman protocol, g=11, p=29, x=5, and y=7. What is the value of the symmetric key?What is the value of R1 and R2?Variations of data g=7, p=23, x=3, and y=5g=5, p=19, x=7, and y=3g=11, p=31, x=3, and y=9g=7, p=43, x=2, and y=7 3. In the Diffie-Helman protocol, what happens is x and y have the same value, that is, Alice and Bob accidentally chosen the same number? Are R1 and R2 same? Do the session key calculated by Alice and Bob have the same value? Explain what would adversary observe? Could she guess Alices and Bobs private key? Use an example to prove your claims. 4. Using RSA scheme, let p=23, q=31, d=457, calculate the public key e. Provide detailed description of all steps, explain what information will be published and what destroyed.Optionally: Encrypt and decrypt simple message M1=100. Variation of data p=23, q=31, d=233p=23, q=31, d=139 5. Suppose Fred sees your RSA signature on m1 and m2, (i.e., he sees (m1d mod n) and (m2d mod n)). How does he compute the signature on each of m1j mod n (for positive integer j), m1-1 mod n, m1 x m2 mod n, and in general m1j m2k mod n (for arbitrary j and k)?
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Cryptography 1. List some of the attacks on the Diffie ...
Lecture 18: Digital Signatures and Security Services
By: Introduction to Cryptography
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Lecture 18: Digital Signatures and Security Services - Video
Lecture 19: Elgamal Digital Signature
By: Introduction to Cryptography
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Lecture 19: Elgamal Digital Signature - Video
The Benefits and Significance of Private Platform as a Service
Facebook has released the source code of a software library that's designed to make it easier for developers to implement fast, secure cryptography in their Android apps.
Dubbed Conceal, the library was developed for a limited range of tasks with the specific needs of Android developers in mind, allowing app makers to include encryption without being cryptography experts.
"Unlike other libraries, which provide a wide range of encryption algorithms and options, Conceal prefers to abstract this choice and include sensible defaults," Facebook engineer Subodh Iyengar wrote in a blog post. "We think this makes sense because encryption can be very tricky to get right."
Facebook hasn't tried to write its own crypto code from scratch. Rather, Conceal takes advantage of a number of cherry-picked algorithms from the industry-standard OpenSSL open source library.
By eliminating the parts of OpenSSL it didn't need, however, Facebook managed to slim down its encryption code to a mere 85KB. By comparison, the full OpenSSL library takes up around 1MB when compiled for ARM chips.
The algorithms that Conceal uses are also fast, even on low-powered ARM chips. In Facebook's own tests on a low-end Samsung Galaxy Y smartphone, Conceal performed significantly better than both stock Java cryptography and the Bouncy Castle library.
Not just easy, but fast: Conceal can encrypt and decrypt data many times faster than other methods
Conceal offers up these algorithms via a simple API that abstracts away most of the choices that other libraries require developers to make. Pass an I/O stream to Conceal, and Conceal returns a wrapped stream that's automatically decrypted or encrypted as it's read or written.
That means Conceal won't be useful for every encryption application, but it will work for a few use cases that crop up frequently on Android. Foremost, it can be used to encrypt data that's stored on SD cards, which is why Facebook invented it in the first place.
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Oi, Android devs! Facebook wants your apps to be more secure
As a graduate student at the Massachusetts Institute of Technology in 1996, Amit Sahai was fascinated by the strange notion of a zero-knowledge proof, a type of mathematical protocol for convincing someone that something is true without revealing any details of why it is true. As Sahai mulled over this counterintuitive concept, it led him to consider an even more daring notion: What if it were possible to mask the inner workings not just of a proof, but of a computer program, so that people could use the program without being able to figure out how it worked?
The idea of obfuscating a program had been around for decades, but no one had ever developed a rigorous mathematical framework for the concept, let alone created an unassailable obfuscation scheme. Over the years, commercial software companies have engineered various techniques for garbling a computer program so that it will be harder to understand while still performing the same function. But hackers have defeated every attempt. At best, these commercial obfuscators offer a speed bump, said Sahai, now a computer science professor at the University of California, Los Angeles. An attacker might need a few days to unlock the secrets hidden in your software, instead of a few minutes.
Secure program obfuscation would be useful for many applications, such as protecting software patches, obscuring the workings of the chips that read encrypted DVDs, or encrypting the software controlling military drones. More futuristically, it would allow people to create autonomous virtual agents that they could send out into the computing cloud to act on their behalf. If, for example, you were heading to a remote cabin in the woods for a vacation, you could create and then obfuscate a computer program that would inform your boss about emails you received from an important client, or alert your sister if your bank balance dropped too low. Your passwords and other secrets inside the program would be safe.
You could send that agent into the computing wild, including onto untrusted computers, Sahai said. It could be captured by the enemy, interrogated, and disassembled, but it couldnt be forced to reveal your secrets.
As Sahai pondered program obfuscation, however, he and several colleagues quickly realized that its potential far surpassed any specific applications. If a program obfuscator could be created, it could solve many of the problems that have driven cryptography for the past 40 years problems about how to conduct secure interactions with people at, say, the other end of an Internet connection, whom you may not know or trust.
A program obfuscator would be a powerful tool for finding plausible constructions for just about any cryptographic task you could conceive of, said Yuval Ishai, of the Technion in Haifa, Israel.
Precisely because of obfuscations power, many computer scientists, including Sahai and his colleagues, thought it was impossible. We were convinced it was too powerful to exist, he said. Their earliest research findings seemed to confirm this, showing that the most natural form of obfuscation is indeed impossible to achieve for all programs.
Then, on July 20, 2013, Sahai and five co-authors posted a paper on the Cryptology ePrint Archive demonstrating a candidate protocol for a kind of obfuscation known as indistinguishability obfuscation. Two days later, Sahai and one of his co-authors, Brent Waters, of the University of Texas, Austin, posted a second paper that suggested, together with the first paper, that this somewhat arcane form of obfuscation may possess much of the power cryptographers have dreamed of.
This is the first serious positive result when it comes to trying to find a universal obfuscator, said Boaz Barak, of Microsoft Research in Cambridge, Mass. The cryptography community is very excited. In the six months since the original paper was posted, more papers have appeared on the ePrint archive with obfuscation in the title than in the previous 17 years.
However, the new obfuscation scheme is far from ready for commercial applications. The technique turns short, simple programs into giant, unwieldy albatrosses. And the schemes security rests on a new mathematical approach that has not yet been thoroughly vetted by the cryptography community. It has, however, already withstood the first attempts to break it.
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Cryptography Breakthrough Could Make Software Unhackable