dr jimbob
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 9h revised Should RSA primes p and q should differ in length by “a few digits”? added 78 characters in body; edited title 10h comment Should RSA primes p and q should differ in length by “a few digits”? @gtrwoot - My guess is it was clear to Rivest et al, that if p and q were too close together there are ways to quickly factor N and undermine the security. They made the recommendation to ensure p and q differed in length by a few digits, so if p is the larger prime and is say 3 (decimal) digits longer you have `p - q ≈ p - p/1000 ≈ .999 p ≈ p ≈ sqrt(N) >> N^(1/4)`. Hence Fermat factorization based on p being near q won't work when p and q differ in length. That said just randomly picking two n/2 bit primes will with high probability result in them being O(sqrt(N)) apart. 10h comment Should RSA primes p and q should differ in length by “a few digits”? 10h comment Should RSA primes p and q should differ in length by “a few digits”? Who said this? It's customary for say 2048-bit RSA to choose two 1024-bit primes that have the same length. That said there are efficient attacks on RSA if p-q is too small. See: en.wikipedia.org/wiki/Fermat%27s_factorization_method or trial division starting from the nearest odd integer to sqrt(N). (This technique is very efficient when |p-q| < O( N^(1/4) ) Apr 30 comment Why is 128bit AES considered very strong but 160bit SHA depreciated? @acidzombie24 - Yes, the security of accepting a particular hash function as part of a validly signing a certificate fundamentally relies on the infeasibility of collision attacks. There's no such thing as "nonsecure bits", it's just a 160 bit hash function takes roughly 2^80 effort to generate a collision to break. This is roughly comparable to the effort to brute-force a block cipher with an 80-bit key. Apr 30 comment Why is 128bit AES considered very strong but 160bit SHA depreciated? @LieRyan - Totally agree. If you look at the edit history the whole idea was introduced by an edit that someone else approved. (Originally I wrote "If say p1 was a certificate for a domain you own and can verify ownership to a CA, you can get a CA to sign it" but was changed to "If say p1 happens to identify any free domain (like phpsdfpspfopo.tv) that you can buy any minute, then you can verify ownership of p1 to a CA and you can get a CA's signature of p1." Granted, changing the domain/subdomain seems a pretty simple way to explain changing `p1` without going to fine details. Apr 29 revised Why is 128bit AES considered very strong but 160bit SHA depreciated? Formatting exponents. Apr 29 revised Why is 128bit AES considered very strong but 160bit SHA depreciated? Formatting exponents. Apr 29 revised Why is 128bit AES considered very strong but 160bit SHA depreciated? added 121 characters in body Apr 29 revised Why is 128bit AES considered very strong but 160bit SHA depreciated? The question asked about SSL certificates. Yes SSL certs use X.509 standard (and we use TLS these days), but it seems overly pedantic to call them that. Apr 29 awarded Good Question Apr 29 revised Why is 128bit AES considered very strong but 160bit SHA depreciated? added 1575 characters in body Apr 29 answered Why is 128bit AES considered very strong but 160bit SHA depreciated? Apr 28 revised What is the problem with multiple encryption and how do you know if you have decrypted a cipher? added 4 characters in body Apr 28 comment What is the problem with multiple encryption and how do you know if you have decrypted a cipher? If two 128-bit keys (`K1`, `K2`) are used to encrypt a message like `c=E(K1, E(K2, m))` then to brute force `c` to recover `m`, you would need to check all the possible combinations of the two keys with a space of (2^128) * (2^128) = 2^(256) possibilities. This is equivalent to brute-forcing a 256-bit key. (Note you said (2^128)^128 which is equal to 2^(128*128) = 2^16384 -- this mistake was originally brought up in another answer by a user named Joe.) Apr 26 comment Why aren't ransomware deployers arrested? @Cestarian - The described doesn't seem foolproof solution against Ransomware. If you accidentally execute malware on any of your machines connected to the NAS and your machine has write privileges to the NAS, then you can be screwed. A good backup policy does (e.g., a privileged account does daily version controlled backups that no one else can write to). Apr 24 answered What is the Javascript trying to do/exploit? Apr 20 comment Does MAC address filtering provide security? I don't see how MAC address filtering reduces the attack surface. OP is clearly asking about wifi (see the wifi tag + wlan0 in example) when the machines being filtered out are directly talking to the router with MAC address filtering. The biggest problem with MAC address filtering in this scenario, is it's easy to find the allowed MAC addresses (by just listening as they are in the unencrypted header of each packet) and it's also easy to change your MAC address. IP address filtering is different, as its not easy for non-network admins to change their IP to allowed ones (at least with TCP). Apr 19 comment Security risks of using MongoDB ID vs a counter in URL? Where in the OPs question did they specify if they are using HTTP? I see them leaving the protocol off of the URL. Apr 19 answered Security risks of using MongoDB ID vs a counter in URL?