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bio website github.com/CodesInChaos
location Frankfurt, Germany
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visits member for 3 years, 5 months
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Mar
6
comment How to calculate the maximum output size for data encrypted with a RSA Private Key?
Oh I missed that you're using encrypting a hash with the private key, that's a bad idea. Use a standard signature algorithm instead. Either with the newer PSS padding or the PKCS1v1.5 signature padding, which unlike its encryption equivalent has no known weaknesses.
Mar
6
comment How to calculate the maximum output size for data encrypted with a RSA Private Key?
I also strongly recommend using OAEP padding over PBKS#1v1.5 padding for RSA encryption. The latter has weaknesses which can be exploited in many use cases and are annoying to work around.
Mar
6
comment How to calculate the maximum output size for data encrypted with a RSA Private Key?
Note that the input size will be smaller, since the padding will take some space.
Mar
6
comment Authenticated encryption without padding
To clarify: You want a transformation that detects modification but doesn't enlarge the ciphertext? That's impossible, since you need some form of redundancy to get detection. The closest you can get with length preserving encryption is that any change to the ciphertext will produce an unpredictable, random looking plaintext. But those transformations are not stream ciphers.
Mar
6
comment Is there a “brainwallet” for GPG keys?
@RobKohr If those were seven random independent words, this is a bit surprising, since I'd estimate that those have 80 bits of entropy or so, which should make it rather expensive to crack. If it was a quote from a book or movie, then they probably mined that source for quotes.
Mar
5
comment How fast can a wrong decryption key be detected using ECC?
@Sibbo bitmessage uses ECIES. This means that ECC is used to produce a shared key, which is then used for encryption (AES-CBC) and MAC (HMAC-SHA-256). A wrong key will lead to a MAC verification failure.
Mar
5
comment Fast modular reduction
@fgrieu I bet they want to do whatever Secp256k1 requires.
Mar
5
comment Long-term data protection, storage of old encrypted traffic and quantum cryptocalipse
@Thomas A big quantum speedup for travelling salesman would be a far bigger revelation than even breaking 4096 bit RSA, since QCs are not believed to solve NP complete problems quickly. D-Wave can solve one specific optimization problem which is closely related to their physical structure. They don't entangle many qubits at the same time, can't run shor, it's dubious that they even offer a quantum speedup for their one favourite optimization problem. In short, D-Wave is useless and not representative of real quantum computers.
Mar
5
comment Long-term data protection, storage of old encrypted traffic and quantum cryptocalipse
@Thomas Just because there are no large quantum computers yet,(don't remember the precise current state of the art, but it's around 5 qubits factoring huge semi-primes like 15) doesn't mean that there won't be such QCs twenty years from now. If you want long term confidentiality QCs resistance should be a consideration.
Mar
5
comment Prime factors of non-random keys
Another related article There’s no need to panic over factorable keys–just mind your Ps and Qs. @fgrieu That paper is pretty high on my list of "dumbest paper titles".
Mar
5
revised elgamal-encryption wiki description
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Mar
5
revised elgamal-encryption wiki excerpt
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Mar
3
comment Three-way hash collision
You get a $2^l$ way collision with cost $l \cdot 2^{64}$. So you get a 16-way collision with cost $2^{66} = 4 \cdot 2^{64}$ not just an eight-way collision.
Mar
3
comment Machine Learning with Encryption
Related questions: Any practical uses of machine learning for cryptography? and Cryptography based upon neural networks
Mar
3
comment Machine Learning with Encryption
You might be able to throw machine learning at side-channel or meta data. But that's a bit beyond crypto per-se.
Mar
3
comment Machine Learning with Encryption
The crypto techniques somewhat related to machine learning that I know of are 1) using SAT solvers as part of cryptoanalysis 2) Learning with error problems in lattice based crypto
Mar
3
comment Check the validity of a rsa key pair with only the public key?
Blind RSA signatures might have some issues if the modulus has a small factors since padded signatures/blinding factors might share factors with the modulus.
Mar
3
comment Derive both MAC and AES keys from same PBKDF2?
@fgrieu I mainly base it on performance, i.e. on the issue describes in that answer. I also think that being able to specify an arbitrary info string is nice.
Feb
28
revised How to calculate the time it'll take to crack RSA or DH?
deleted 67 characters in body; edited tags
Feb
28
revised Solving a discrete logarithm using GDlog
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