Cryptography Weekly Newsletter - Tuesday, September 30, 2014

Cryptography newsletter

Top new questions this week: Why should CAST5 and 3DES not be used for encrypting files over 4GB? On https://www.gnupg.org/faq/gnupg-faq.html#define_cast, it says that Like 3DES, its 64-bit block size means it should not be used to encrypt files larger than 4Gb in size… How and why does the … block-cipher 3des blocksize   asked by Michael 7 votes answered by owlstead 7 votes Is deniable error-correction possible? This question came up as I tried to answer an earlier question I asked: cryptographic data structure wanted: sparse array without membership test. I still have not resolved that question to my … algorithm-design   asked by gmr 7 votes answered by David Cary 3 votes Is there benefit to signing unencrypted emails? I came to this article from another comment on Crypto StackExchange. After reading it, I am wondering if there is any benefit to using a digital signature on unencrypted S/MIME emails? encryption signature s-mime   asked by Nikolay Spassov 6 votes answered by Jason Callaway 8 votes SHA1 no longer considered secure for SSL Certificates -- what about Cipher Suites? Many browsers and Internet companies have recently claimed that SSL Certificates with a signature algorithm of SHA1 will imminently no longer be considered secure. Most notably, Google and Google … ssl sha-1 sha-2   asked by Eddie 4 votes answered by otus 4 votes Is there any area where AES-CBC cannot be used ? If so, why ? I would like to know the domains or specific applications where using AES-CBC is not advised due to any drawbacks like sequential encryption of AES-CBC ? aes algorithm-design modes-of-operation cbc   asked by rijndael 3 votes answered by owlstead 14 votes NIZK Proof of knowledge N of M discrete logarithms (threshold) It is well known how to produce a NIZK that curvepoints $aG$ and $aP$ have the same discrete logarithm $a$ with respect to the curvepoints they are multiplied by. There is also a way to prove that a … discrete-logarithm zero-knowledge-proofs threshold-cryptography   asked by Andrew Poelstra 3 votes answered by DrLecter 1 vote Message encrypted with a LFSR based stream cipher I am learning about LFSR sequence and I came across this question: A 16-bit message consists of two ASCII characters. This message was encrypted with a one-time pad, and the key for the one-time pad … stream-cipher lfsr   asked by J0ker 2 votes answered by mczraf 1 vote Greatest hits from previous weeks: Difference between stream cipher and block cipher A typical stream cipher encrypts plaintext one byte at a time, although a stream cipher may be designed to operate on one bit at a time or on units larger than a byte at a time. A block cipher … encryption block-cipher stream-cipher   asked by Ravindra Bagale 7 votes answered by Paŭlo Ebermann 8 votes HMAC-SHA1 vs HMAC-SHA256 I have three questions: Would you use HMAC-SHA1 or HMAC-SHA256 for message authentication? How much HMAC-SHA256 is slower than HMAC-SHA1? Are the security improvements of SHA256 (over SHA1) enough … hash hmac sha-256 sha-1 sha-2   asked by Mario 3 votes answered by poncho 9 votes Can you answer these? Encrypted database: how to deal with general queries? My question is quite related to the concept of homomorphic encryption, which is not practical at all nowadays. In short, I would like to know how to query encrypted databases. Simple queries which … encryption homomorphic-encryption database   asked by mczraf 2 votes See any problems with this search-specific homomorphic encoding strategy? I'm imagining this for use in the scenario of cloud-stored client-encrypted email, where, when seeking to do a string search across messages, you don't want to have to download every stored message in … homomorphic-encryption searchable-encryption   asked by Mike Lawrence 1 vote What is the (uncompressed) x,y-representation of a curve point on the P-256 NIST elliptic curve? I am trying to understand the FIDO U2F Raw Message Format, especially the format in which a user public key should be provided. The documentation says the following: A user public key [65 bytes]. … elliptic-curves   asked by mritz_p 1 vote

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