CodesInChaos

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bio website github.com/CodesInChaos
location Munich, Germany
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Apr
25
 comment How to sign a message using RSA?
Look into the relevant Mono classes. With a bit of work, many of them work on .net, and the license is permissive.
Apr
25
 comment How to sign a message using RSA?
Read PKCS#1, in particular don't ignore the part about padding.
Apr
25
 comment Questions about Key Derivation Functions
Your description is a bit vague. But I assumed that with ` AES(⋅,m)` you meant putting the master key into m and using the purpose as key. And that's clearly a bad idea.
Apr
25
 comment Questions about Key Derivation Functions
"Would AES(⋅,m) for a fixed m be equivalent?", no since it's reversible. The purpose/counter is known, and since you use it as key, the message can be recovered from any K_i, and then you can derive all other K_j.
Apr
25
 comment Identifying cryptography cipher
At least you posted the source, and not just a random bunch of bytes, like most that ask such a question do
Apr
25
 comment Can a proof be constructed to show there is no distinguisher?
There is at least some PRNGs for which proofs exist that show that they're indistinguishable provided a certain other problem is hard. en.wikipedia.org/wiki/Blum_Blum_Shub
Apr
24
 answered Existing dictionaries of popular words to help solve a random substitution cipher?
Apr
23
 comment Question about hash collisions
@Mads yes of course.
Apr
23
 revised Question about hash collisions
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Apr
23
 revised Question about hash collisions
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Apr
23
 revised Question about hash collisions
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Apr
23
 answered Question about hash collisions
Apr
23
 comment Question about hash collisions
If you extend this scheme directly to a tree-hash it will be trivially vulnerable to collisions with a different length. That's why tree-hashes typically use a different hash function for inner hashes and leaf hashes.
Apr
23
 comment Existing dictionaries of popular words to help solve a random substitution cipher?
List of words occuring in en.wikipedia ordered by popularity: the-interweb.com/serendipity/index.php?/archives/…
Apr
22
 comment How secure is the Vigenère cipher in file encryption if you encrypt the password first?
@Ephraim If you want to go that way, you should simply use an existing stream cipher.
Apr
22
 comment Can a digital money system exist, that's secure, anonymous and allows offline transactions?
While I don't really like such schemes(I already described it in the question as one that falls a bit short of my expectations), it's probably the best thing you can get if you want offline spendability, so I'll accept this answer. My personal consequence is that offline spendability should be sacrificed, in favor of higher anonymity, and in protocol enforceability.
Apr
22
 accepted Can a digital money system exist, that's secure, anonymous and allows offline transactions?
Apr
22
 comment Can a digital money system exist, that's secure, anonymous and allows offline transactions?
1) I'm not interested in quantum schemes 2) I understand that payments are untraceable in the ideal case, thanks to blind signatures. But in order to get the name embedded into the tokens, I need to register each payment I send/receive with my bank in my name, even if the bank doesn't learn who was the partner in the transaction. 3) An honest mistake can also easily lead to deanomymization via double-spend. For example you restore from backup, or your application crashes at an unfortunate time. 3) It also leads to unbounded financial risk for the victim if somebody steals the tokens
Apr
22
 revised Which blind signature schemes exist, and how do they compare?
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Apr
22
 revised Blind signature with openssl
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