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I SHALL DEVOUR YOUR HEART AND FEAST ON YOUR SOUL (so don't bug me).


Jul
29
comment Adding SSL to existing applications
I am using the term "SSL" as the generic term for the whole family (especially when responding to someone who apparently does the same). See this for details.
Jul
28
comment Conflict between cipher-suite and certificate
From here, ssl.gstatic.com uses a certificate that contains an EC public key, so everything appears to be in order.
Jul
24
comment For maximum security is it best to link OpenSSL libraries statically or dynamically?
There is reputedly only one software without bugs (Metafont, written by Donald Knuth). It is possible to write safe C code by being careful; but, apparently, it is not humanly possible to be sufficiently careful throughout the whole development of any significant piece of software. However, competent programmers can be good at leaving few bugs, and fixing them promptly when detected. Which is enough in practice, as long as the patch installation process is sleek and slight (hence dynamic linking).
Jul
22
comment How much entropy is good enough for seeding a CSPRNG?
If your CSPRNG is really CS, you do not need to use several of them (if that was a problem, then your CSPRNG would not be really CS).
Jul
22
comment How bad an idea is intentionally using short RSA keys for signing CloudFront private-content URLs?
@AaronD: that's the point: we are not talking about encryption but signatures. If a new key is generated every day, then it does not matter if an attacker breaks a key that was used two years before -- it won't be accepted anyway. This highlights that encryption and signatures use really distinct security models.
Jul
21
comment How to steganograph ownership information into members uploaded images?
Well, watermarking does not have to be obvious; in fact, we prefer it when it does not deteriorate the picture's main functionality, i.e. "being looked at". But, contrary to steganography, it is not a problem if the watermark is known to be there (in fact it is often the point: to deter copyists by making it known that there is a watermark).
Jul
21
comment How to steganograph ownership information into members uploaded images?
"watermarking is a lot harder to do than steganography". Yes, I think that I meant to say that, and also that I actually did.
Jul
21
comment Is it complicated to deploy my own CA?
There is no such thing as a definitive, authoritative source for English typography (contrary to, say, French typography, because the French, in all their frenchness, created an Académie Française whose job is to be Right, always). Using a space before the question mark is relatively rare but not unheard of among English writers. It is often said to mimic French punctuation. The question mark itself is a relatively recent import into English (circa 1580, say some authors). Bottom-line: it is not absolutely incorrect to put a space; and I find it clearer that way.
Jul
19
comment do serial numbers for x509 certs need to be sequential or can they be timestamp's?
There is an official recommendation: for backward compatibility with some deployed implementations, the serial number encoded value should fit in 20 bytes -- thus you can use integers up to 2^159 (DER encoding of an INTEGER is signed, so there must be room for a sign bit).
Jul
17
comment Is it good practice to send passwords in separate emails, and why?
Most "best practices" are old lore turned into dogma through sedimentation, and parroted by people who like to think of themselves as "cybersecurity experts".
Jul
17
comment What Country, State and City should I choose when requesting an SSL certificate?
Theoretically, a PKCS#10 certificate request is supposed to be signed with the corresponding private key; this is called a "proof of possession" (i.e. you may request a certificate with a given public key only if you actually control the corresponding private key). What you would gain from buying a certificate with the public key of somebody else is unclear. Also, this self-signature cannot work for an encryption-only key (e.g. Diffie-Hellman). Many CA will verify the self-signature, mostly out of Tradition.
Jul
17
comment What Country, State and City should I choose when requesting an SSL certificate?
A PKCS#10 certificate request contains the public key you want to see appear in the certificate. It may contain a lot of other things (it is an extensible format, with extensions) but the CA is free to pick what it wants from the request and ignore the rest. The public key is about the only thing that the CA necessarily uses from the request, and most CA will use only that and ignore the rest.
Jul
17
comment What Country, State and City should I choose when requesting an SSL certificate?
There is no standardized method for the CA to put in the certificate the parts of the requests that it does not want to put in the certificate. If you take my meaning. Basically, if the CA decides to fully ignore the name you provided, then it fully ignores that name and you won't see it anywhere.
Jul
17
comment Guessing random bit with 100% accuracy
Yeah, I was so pleased with myself for thinking about this (I mean, even more pleased that I usually am) that I failed to notice that without this side-channel I actually had the correct answer.
Jul
17
comment Guessing random bit with 100% accuracy
Probability of success is 75% is both programs answer randomly (since the prize is obtained when either or both guesses correctly).
Jul
14
comment Electronic identity and digital signatures - why they are different?
I am in support of the same key for two operations when (and exactly when) it makes no sense to have two separate keys. I know, however, that there are people who like to overdo things and insist on multiple keys even in cases where it does not make any good.
Jul
14
comment Is RC2-CBC at all secure?
Well, for emails, there is no return path. SSL clients and server can negotiate cipher suites, but when you send an email it should work first time. Theoretically, people can send "S/MIME preferences" that contain their public key (certificates) and supported algorithms, but I am not sure I really saw that work even once.
Jul
13
comment How do I prepare for Certificate Authority end of business?
If the last available CRL has a nextUpdate field in the past, and no newer CRL is produced by the CA, then systems that validate the certificates ought to reject them, because "certificate revocation status cannot be ascertained". Web browsers are an exception, since they just don't really bother honouring revocation.
Jul
13
comment Password rules: Should I disallow “leetspeak” dictionary passwords like XKCD's Tr0ub4dor&3
My main point is that users should select non-weak passwords on their own volition -- the more rules you enforce, the more users will find creative ways to generate weak passwords, instead of producing strong passwords. However, the system must still project the idea that strong passwords are important, and a minimal length is, in my view, the best compromise: not too harmful since users are ready to accept such a limitation (they feel that they understand it), and still a good conveyor of the idea that there is such a thing as security.
Jul
12
comment Password rules: Should I disallow “leetspeak” dictionary passwords like XKCD's Tr0ub4dor&3
@SteveJessop: by my logic there should be no lower limit on password length. However, if the system accepts (for instance) three-letter passwords, then quite a lot of users will feel invested with the sacred mission to warn you (the sysadmin) about the folly of three-letter passwords, and simply reading all these complaints will consume a lot of time. Enforcing a minimal length is something that average users understand and accept, and serves as a signal that you actually mind security.