13,651 reputation
33372
bio website paul-ebermann.tumblr.com
location Berlin, Germany
age
visits member for 3 years, 6 months
seen 2 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
30
comment Encryption scheme for social-network-like data sharing data via untrusted server?
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
30
revised Encryption scheme for social-network-like data sharing data via untrusted server?
edited tags
Sep
29
comment Where can I get information on how to implement AES?
Just a note: For productive use, you often want to use existing implementations instead of creating your own, since they probably are better shielded against side-channel attacks, and might also be more efficient (e.g. might use AES-specific instructions on modern processors). For learning about the internal workings it is a good idea to implement it yourself, though.
Sep
29
comment Can ECDSA signatures be safely made “deterministic”?
@ThomasPornin Ah, thanks. Looks like I mixed $k$ and $r$.
Sep
29
revised How did the Koblitz/Menezes papers affect the cryptography community?
add titles of these papers
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?