123 reputation
4
bio website acooke.org
location Santiago, Chile
age
visits member for 2 years, 2 months
seen Dec 2 '13 at 23:34

I work on projects that mix computing and physics - I have a pile of experience as a software engineer, but my education, way back in the day, was as an astronomer. And it was research in astronomy that first took me to Chile, where I now live. So I telecommute from Santiago, working with companies in the USA and UK. Currently I'm part of a small team developing software related to geophysics - I guess you could call it a consultancy, but really we're just people that understand what you need and then - importantly! - make it.

Some of my favourite answers:

In every case I learnt something new, which is what's so good about this site :)


Nov
25
comment How is the MD2 hash function S-table constructed from Pi?
@user8911 - they are not pi. the question is how the fractional part of pi is used to derive a permutation of 0...255
Nov
25
comment How is the MD2 hash function S-table constructed from Pi?
if you take the first 256 bytes from the binary fractional part, and order them, is the first byte in the 41st position, maybe?
Dec
30
comment Future-Proof Versioning and Validation
@JesperMortensen afaik keyczar doesn't work w python 3. if it does, please tell me. incidentally, simple-crypt is secure against that attack and it's documented in the code (not through any brilliance of mine, but because i have been pestering people to review the code and including their feedback)
Dec
28
comment Future-Proof Versioning and Validation
@Thomas oh, an extra HMAC (one that doesn't change with protocol ID), sorry, right.
Dec
27
comment Future-Proof Versioning and Validation
i don't have a specific attack in mind (hence my comment that maybe i need to wait for more specifics). i'm just assuming i may have screwed up. thanks for the comments - it's given me more to think about. i'll wait a while to see if anyone else posts, but that was help enough for a "correct" answer, thanks.
Dec
27
comment Future-Proof Versioning and Validation
thanks. so apologies for not being clear enough that what seems to be the root of the problem is that i want to both (1) automatically support decrypting data encrypted with an older version and (2) somehow avoid attacks that supporting an older version could imply. i guess looked at that way i may be asking the impossible. to answer the final q - the api is ideally two functions, encrypt and decrypt. but maybe i need to consider conversion instead of automatic backwards support. ps the current heder includes what you are calling a protocol id.
Dec
27
comment Future-Proof Versioning and Validation
@dchest - true, but in general corrupting the data will simply abort things. changing the version number triggers a more specific action (update your software) that might be combined with some kind of attack where a fake replacement is provided. i realise i may be taking things too far, but it seemed like it was different...
Dec
27
comment Future-Proof Versioning and Validation
@PaĆ­loEbermann - yes, clarified