9,417 reputation
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bio website github.com/CodesInChaos
location Frankfurt, Germany
age
visits member for 3 years
seen 9 hours ago

Apr
20
comment Offline anonymous electronic money systems and their cryptographical base
Are you sure such a system can even exist? I think that out of secure, anonymous and offline, you can only have two at the same time.
Apr
18
comment How can I do a brute force (ciphertext only) attack on an CBC-encrypted message?
Do you know which padding mode was used, and how long the plaintext and/or ciphertext are?
Apr
18
comment Is RSA of a random nonce with no padding safe?
@ThomasPornin Your argument doesn't show that per-encryption randomness is required. For example you don't show why padding based on hash(m,e,n) is a problem. Such a scheme is still deterministic, and doesn't suffer from this specific problem.
Apr
18
comment Why is elliptic curve cryptography not widely used, compared to RSA?
For me the primary selling point of RSA is that it doesn't leak the private key if your PRNG happens to be badly seeded while signing. While it's possible to avoid this issue, most implementations don't.
Apr
18
awarded  Scholar
Apr
18
accepted Can one reduce the size of ECDSA-like signatures?
Apr
16
comment Deterministic nonces in CTR mode
There is already a question about the first scheme, so this question is mainly about the second scheme. In particular how it compares to the first scheme.
Apr
16
revised Can one reduce the size of ECDSA-like signatures?
added 52 characters in body
Apr
16
comment Deterministic nonces in CTR mode
@MartinSuecia In this scheme(assuming no password is used) knowledge of the plaintext hash trivially reveals all of the plaintext, since it effectively doubles as encryption key. @-Henrick Files are immutable in such a scheme, but convergent encryption is inherently vulnerable to certain confirmation attacks.
Apr
16
comment Deterministic nonces in CTR mode
@HenrickHellström You need to get that hash for an outside source, typically it's part of the download link. This is a scheme similar to freenet's CHK or tahoe-lafs immutable files.
Apr
16
awarded  Tag Editor
Apr
16
revised ctr wiki excerpt
added 104 characters in body
Apr
16
suggested suggested edit on ctr tag wiki excerpt
Apr
16
suggested suggested edit on ctr tag wiki
Apr
16
wiki created ctr excerpt
Apr
16
awarded  Student
Apr
16
comment Deterministic nonces in CTR mode
The AES key will be as unique as random 128 bit numbers are. It's derived from the hash of the plaintext file, optionally combined with a password.
Apr
16
asked Deterministic nonces in CTR mode
Apr
16
asked Can one reduce the size of ECDSA-like signatures?
Apr
15
comment Can RSA encryption produce collisions?
"if your message is small m^e will be smaller than the large N." Since m is the padded message, this won't happen in practice.