13,596 reputation
33272
bio website paul-ebermann.tumblr.com
location Berlin, Germany
age
visits member for 3 years, 5 months
seen 15 hours ago

Don't fear to edit my posts: even if I have more reputation than you, I do make mistakes.

I'm now also a Moderator Pro Tempore (= until the first elections) at Cryptography Stack Exchange: feel free to come around and ask some cryptography questions.


My personal name is spoken as /ˈpawlo/ (IPA), in English this would be written similar to Powlo, I think (i.e. the vowels are ow and o), with an accent on the before-last syllable (which is the first in this case). It's the Esperanto form of my given name.

The photo shows my shadow, taken at night. My camera sometimes seems to forget all the other frequencies and only stores the green ones.

My current main private programming project is the game of fencing, an online abstract turn based strategy game. Implemented as a Java applet, using git as a version control system.


Some more links:


Sep
29
comment Can ECDSA signatures be safely made “deterministic”?
I don't see why you want to include the private key in the generation of $k$.
Sep
29
comment Is there a secure cryptosystem that can be performed mentally?
This is not really an encryption - it is missing a key. One could make it a cipher by making the "180°" into a key (i.e. make this a variable number instead, like $x$ clock positions to the right). It still is a quite weak cipher even then, and relies mostly on security-by-obscurity (i.e. that the adversary does not know the algorithm).
Sep
29
revised Is there a secure cryptosystem that can be performed mentally?
inline the link, make the apology smaller
Sep
29
reviewed Approve Is there a secure cryptosystem that can be performed mentally?
Sep
28
comment What is wrong with using SHA1 in digital signatures? Why is a robust hash function needed?
You could use the key as an input to the hash function (which means that one can only generate the hash if one has the public key – Skein has a special mode for this), but this will not help against weaknesses of the hash function. – Normally we simply assume the hash function is good enough. (For long-term signatures, maybe combining two different hashes would give a bit more resistance against breakthroughs.)
Sep
28
comment What is wrong with using SHA1 in digital signatures? Why is a robust hash function needed?
Yes, exactly. (Or you could say you signed something else, showing the forged document.)
Sep
28
comment Is it possible to create an asymmetric cryptosystem where the private keys are not easily verifiable as such?
Actually, $p$ and $q$ are normally private, too, having them allows simply calculating $d$ from $e$ (by the formula you show).
Sep
28
revised Is it possible to create an asymmetric cryptosystem where the private keys are not easily verifiable as such?
add link title, remove boilerplate
Sep
28
comment What is wrong with using SHA1 in digital signatures? Why is a robust hash function needed?
If the hash is broken (in the second-preimage sense), anyone who has the message can construct a second message which has the same hash, where thus the same signature will be valid. This person doesn't even need the public key or the original signature.
Sep
28
revised How can we reason about the cryptographic capabilities of code-breaking agencies like the NSA or GCHQ?
some punctuation
Sep
28
answered What is wrong with using SHA1 in digital signatures? Why is a robust hash function needed?
Sep
28
comment What is wrong with using SHA1 in digital signatures? Why is a robust hash function needed?
Welcome to Cryptography Stack Exchange. Your question was migrated here because of being not directly related to software development (the topic of Stack Overflow), and being fully on-topic here. Please register your account here, too, to be able to comment and accept an answer.
Sep
28
revised What is wrong with using SHA1 in digital signatures? Why is a robust hash function needed?
typo, formatting
Sep
28
revised What is wrong with using SHA1 in digital signatures? Why is a robust hash function needed?
edited tags
Sep
28
comment Is there a secure cryptosystem that can be performed mentally?
I suppose "Pen & Paper" is much more easily done than "mentally". Would such answers be welcome, too?
Sep
28
revised How does HOTP keep in sync?
Really have the wikipedia link, hotp tag
Sep
28
comment What is wrong with using SHA1 in digital signatures? Why is a robust hash function needed?
Nah, there are infinitely many possible meaningful documents, but only 2^160 different possible SHA-1 hashes. By only varying some short sections of a document (in total a bit over 80 bits long, for example some numbers in non-important cells of the spreadsheet), you are bound to get collisions with sensible documents. Of course, this (with a secure hash function) still takes too much time to be done in the attacker's lifetime.
Sep
28
revised Why can't Diffie-Hellman be used for signing?
edited tags
Sep
28
comment What is wrong with using SHA1 in digital signatures? Why is a robust hash function needed?
Actually, the "should be wildly different" is more like "it is hard to find two such documents at all" (but then you could quite likely have lots of spreadsheets differing only in some of the numbers in the cells).
Sep
28
revised For Diffie-Hellman, must g be a generator?
formatting the quote as such