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Aug
17
revised How can I fix a corrupted PGP file?
fixed title's grammar
Aug
17
comment Is my id obfuscation algorithm secure?
Even if they're not interested in forgeries, an adversary might want to submit its own ciphertext as part of trying to trace specific chips. $\:$ For equation (1) on page 4 of the swap-or-not paper, N is $2^{48}$, $r$ would be 500, and $q$ would be [[[number of encryptions per chip] times [number of chips]] plus [number of additional ciphertexts that an adversary might submit]]. $\;\;\;\;$
Aug
17
comment Is my id obfuscation algorithm secure?
@Ozo : $\:$ That depends mainly on how many encryptions and decryptions you might do. $\;\;\;\;$
Aug
16
comment Is my id obfuscation algorithm secure?
cs.ucdavis.edu/~rogaway/papers/shuffle.pdf $\:$ eprint.iacr.org/2013/560.pdf $\;\;\;\;$
Aug
16
revised How to perform authentication without central server in P2P?
improved grammar and changed spacing
Aug
15
comment How does the signature checking work in DKIM?
Have you tried looking up digital signatures? $\;$
Aug
12
revised Luby-Rackoff theorem confusion
fixed typo and changed spacing
Aug
12
comment Is prime regeneration necessary for every new session using a Diffie-Hellman key exchange?
"changing $g$ and $P$" can "help matters" by making an adversary use the black box for each $\hspace{.77 in}$ session it wants to attack, after seeing the whole key agreement. $\;$
Aug
12
revised Security implication of exporting private key
fixed typo and changed spacing
Aug
12
comment Is there an encryption that is only reversible with a key?
crypto.stackexchange.com/q/292/991 $\;$
Aug
12
comment Security issues of a MAC-then-Encrypt-then-MAC approach?
Even with HMAC (or any scheme whose tagging algorithm is deterministic), e-sushi's $\hspace{1 in}$ suggestion would leak equality of plaintexts. $\;$
Aug
11
comment Are there any cryptographic flaws in my webhook signing process?
A server certificate plus a password is a way "short of Client SSL Certificates" "to know $\hspace{1.12 in}$ that the sender of the HTTP call is who we think they are". $\;$
Aug
11
comment Computational Complexity - When is it really exponential time?
@polarbear : $\:$ That's why we "view matrix multiplication relative to the size of the" $\hspace{1.2 in}$ matrices (since those are the inputs). $\;\;\;\;$
Aug
11
comment Do I need to use AE/AEAD in my particular scenario? Or is it redundant?
I would heuristically expect that to hold for RSA even if the public keys are not known to attackers, since I would expect signatures to be distributed roughly uniformly in {1,2,3,4,5,...,modulus-1}. $\:$ On the other hand, it is provably the case that if there are are secure signature schemes then there are secure signature schemes for which the signatures do not provide signer anonymity even against parties that don't have any of the verification keys. $\:$ Also, "messages cannot be repudiated by senders" is a feature (see the upper #3 in the OP). $\;\;\;\;$
Aug
11
comment Do I need to use AE/AEAD in my particular scenario? Or is it redundant?
The OP's scheme also does not provide signer anonymity against eavesdroppers. $\hspace{1.55 in}$
Aug
11
comment Do I need to use AE/AEAD in my particular scenario? Or is it redundant?
You're missing that you still haven't edited your question to specify that the author will be signing with the author's private key instead of encrypting with the author's private key. $\;$
Aug
11
comment Do I need to use AE/AEAD in my particular scenario? Or is it redundant?
The main problem is that I'm not aware of any reason(s) it should be hard to have a significant probability of finding an asymmetric encryption of a random message's digest-hash. $\;$
Aug
11
comment Do I need to use AE/AEAD in my particular scenario? Or is it redundant?
@P.T. : $\:$ Do you mean a symmetrically encrypted hash, or one that was encrypted $\hspace{1.35 in}$ "with the message author's private key"? $\;\;\;\;$
Aug
11
comment Do I need to use AE/AEAD in my particular scenario? Or is it redundant?
Even after your edit, your post does not mention signing. $\:$ A commitment to the AES key needs to be included in what gets signed, since otherwise the receiver could break non-repudiation by claiming a different AES key. $\:$ Additionally, there needs to be only one way to split what gets signed back into its parts. $\:$ (If at most one part is not fixed-length, then the previous sentence will automatically be satisfied.) $\;\;\;\;$
Aug
11
comment Do I need to use AE/AEAD in my particular scenario? Or is it redundant?
Yes, since encrypting the digest-hash with the message author's private key is not necessarily useful. $\:$ Instead, the author should presumably sign the output from (2) with the author's private key. $\hspace{.95 in}$