Jalaj

875 reputation

bio	website
	location	Waterloo, Canada
	age	28
visits	member for	1 year, 6 months
	seen	Jan 20 at 4:30
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I am a PhD student with an interest in theoretical cryptography and mathematical tools used for cryptanalysis.

	875 reputation	bio	website		visits	member for	1 year, 6 months
27 badges		location	Waterloo, Canada		seen	Jan 20 at 4:30

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Jan 27	answered	RS Erasure Coding and Shamir's Secret Sharing
Jan 27	revised	Designing a key expander out of ciphers deleted 10 characters in body
Jan 27	comment	Designing a key expander out of ciphers My idea is to use the same resilient function to encrypt as well. Since the output of the resilient function is uniform even if $n-1$ input are fixed, we can use $y$ as one of the uniformly randomly picked value and rest of the value some fixed $IV$, just like hash function. Once we do this, we get two random values. We can use a $n,1,n-2$ or the same old resilient function with $y$ and last iteration output as the randomly chosen input and rest as $IV$ and so on. The resilient function is a public knowledge, so it can act as the encryption scheme. I see it is like iterated hash function!
Jan 26	revised	Designing a key expander out of ciphers added 8 characters in body
Jan 26	comment	Designing a key expander out of ciphers You reformulated the question like that. Alice is given $n$ ciphertexts, one of them is secure, and hence the corresponding encryption scheme satisfies the indistinguishability definition of the security, hence the output of that encryption scheme is uniform, giving me the $1$ variable to construct the $n-1$ resilient function. Once $y$ is computed, Alice keeps on re-encrypting $y$ using the key, $k$, $i+1$ times to get $i^{th}$ key. Now on the part of Bob, since he knows $k$, he can generate the keys in decrypting the $n^{th}$ encryption that corresponds to $n^{th}$ key and so on.
Jan 26	answered	Designing a key expander out of ciphers
Jan 26	revised	Provable Encryption added 12 characters in body
Jan 26	answered	Provable Encryption
Jan 26	answered	How can I repeatedly prove I have data another has seen without sending the data and without the other storing the data?
Jan 25	comment	How to construct encrypted functions (with either public or private data)? I am glad that I was able to clear my remarks. Actually, I had a discussion with Vinod when he was visiting my university last term on the history of FHE and its application. I remember him citing evoting, private function evaluation, $\mathsf{CRHF}$, and $\mathsf{PIR}$ as pure applications of FHE or rather put in his words, "the holy grail of cryptography!"
Jan 25	answered	Stretching a random seed to maximize entropy
Jan 23	comment	How to construct encrypted functions (with either public or private data)? I am talking about "motivation" and why people cared about FHE. All other applications are just a bonus. I can cite thousands of examples. Another famous example is one-way function. They were motivated to do cryptographic task, but they are one of the key ingredients in proving many complexity-theoretic results as well. In fact, their explicit existence will resolve the famous $\mathsf{P}$ Vs $\mathsf{NP}$ problem! But this, by no means suggest that OWF was coined to prove $\mathsf{P} \neq \mathsf{NP}$. This would be plain wrong. Natural proofs and Relativatization were done for that purpose.
Jan 23	comment	How to construct encrypted functions (with either public or private data)? I went through Section that you mentioned. It clearly says, "With FHE, some functions can be evaluated privately" and this is exactly what I mentioned in my comment. You may evaluate private function using FHE, but FHE was not motivated to do this. The paper I mentioned does exactly the same! Primitives are developed and their applications are found later on. For example, PSG are used to construct randomness extractor, but well, PRG was not developed to do that task: the prime motivation of PRG was to derandomize $\mathsf{BPP}$. There are many such examples.
Jan 23	awarded	Commentator
Jan 23	comment	How to construct encrypted functions (with either public or private data)? I just read the abstract and the first page of the introduction. This paper also concerns with only performing some circuit operation (publicly known) on encrypted data. It does not perform publicly known data on private circuit. It does not say that the motivation of constructing a FHE is to compute private functions. The prime motivation was to compute public function on encrypted data.
Jan 21	comment	How to construct encrypted functions (with either public or private data)? You may require homomorphic encryption to do the task, but homomorphic encryption is not constructed to perform the task. For example, Mohassel had a paper in CANS 2011 titled "Fast Computation on Encrypted Polynomials and Applications" which if I remember correctly performs the task of evaluation of encrypted polynomial by using additive homomorphic encryption scheme. You can find work on this line, but sure enough, homomorphic encryption is devised to evaluate a publicly known circuit on encrypted data, nothing more than that!
Jan 19	comment	Is it possible to figure out the public key from encrypted text? Ohh yes! Sorry, I misunderstood it. Thanks for the clarification.
Jan 19	comment	Is it possible to figure out the public key from encrypted text? The question is whether Eve can find the public key and not the private key.
Jan 19	comment	Is it possible to figure out the public key from encrypted text? Your reduction seems to be on the following line: If she can guess $e$, then she can compute $N$ and hence the factorization of $N$. Since the latter problem is assumed to be hard, we see that we have a contradiction and hence it should not be possible for Eve to find out the public key by looking at the plaintext and the corresponding ciphertext. So, I think you proved that it is not possible to guess the value of $e$. Correct me if I am wrong.
Jan 18	awarded	Critic