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comment Checking my crypto — encryption of file contents using AES-256 in CBC mode w/HMAC authentication
The exact file size is more than CBC mode reveals, although that doesn't "compromise the encryption". $\:$ However, your encryption procedure uses pbkdf2 on the same "password" with different salts that are both known to the adversary, rather than just using it once and then applying a pseudorandom generator (such as a hkdf) to the key obtained from pbkdf2. $\:$ Also, I don't see any reference to iterations in your post. $\hspace{.3 in}$
1h
comment Non-repudiation and digital signature of a dishonest participant
(My initial comment shouldn't have said "also". $\:$ The issue raised in your OP is $\hspace{1.5 in}$ hardly "fundamental", it's just an important subtlety.) $\;\;\;\;$
1h
comment Checking my crypto — encryption of file contents using AES-256 in CBC mode w/HMAC authentication
Make sure you are in fact skipping the mode's default unpadding (the library should have a way to do that), due to the risk of a padding oracle. $\;$
2h
comment Checking my crypto — encryption of file contents using AES-256 in CBC mode w/HMAC authentication
"CBC mode" $\: \mapsto \:$ "CBC mode without unpadding" $\;\;\;$ ? $\;\;\;\;\;\;\;\;$
2h
comment Checking my crypto — encryption of file contents using AES-256 in CBC mode w/HMAC authentication
Are the formats of the first two inputs such that if $pwdConcat0 = $pwdConcat1 then $\hspace{.52 in}$ $pwd0 = $pwd1 and $srvFilePath0 = $srvFilePath1 and $\hspace{1.28 in}$ $realFileName0 = $realFileName1? $\:$
2h
comment Checking my crypto — encryption of file contents using AES-256 in CBC mode w/HMAC authentication
Does . represent concatenation? $\:$ Should "context" be replaced with "contents"? $\hspace{1.35 in}$
2h
comment Non-repudiation and digital signature of a dishonest participant
... key agreement usually doesn't need nonrepudiation. $\;$
3h
comment Non-repudiation and digital signature of a dishonest participant
The most generic way is a (physically) signed contract stating that, in return for something, Alice will be bound to a certain extent by signed messages that are compatible with [specific public key]. $\:$ One potential alternative is a (video-and-audio) recording of Alice stating that she will be bound to a certain extent by signed messages that are compatible with [specific public key]. $\;\;\;\;$
3h
comment Non-repudiation and digital signature of a dishonest participant
Yes. $\:$ That issue is also fundamental for nonrepudiation, but it's independent $\hspace{1.75 in}$ of the issue raised in your opening post. $\;\;\;\;$
4h
answered Non-repudiation and digital signature of a dishonest participant
19h
comment Parallel Pollard's Rho: Number of distinguished points
Oh, I'd missed that part. $\;$
20h
comment Parallel Pollard's Rho: Number of distinguished points
journals.kantiana.ru/eng/vestnik/860/2408 $\;$
1d
answered One-way function definition
Jan
28
comment RSA: How effective is this keypair-trash attack
There is an even "more annoying scenario" than that: "compute the gcd of" each pair $\hspace{1.32 in}$ of "public keys you can scan over the net." $\;$
Jan
28
answered How do I communicate the value of the initialization vector to the end user? Should it be part of the encrypted message?
Jan
28
comment How do I communicate the value of the initialization vector to the end user? Should it be part of the encrypted message?
From the short description you gave of the assignment, it sounds like you don't need to implement a mode of operation. $\:$ For modes of operation (including CBC), you would store the initialization vector as the beginning of the ciphertext, so that the decryption algorithm can do what you describe. $\;\;\;\;$
Jan
28
comment How do I communicate the value of the initialization vector to the end user? Should it be part of the encrypted message?
"to implement a 32-bit block cipher" for which a specification was given, or one chosen by you? $\hspace{.6 in}$ "a simple block-cipher that uses CBC" is possible, although it seems far more likely that you mean "CBC mode with a simple block cipher", especially since you then jump straight into talking about IVs. $\hspace{.6 in}$
Jan
28
comment Negative exponents in Shoup's threshold RSA?
x^(-n) = x^((-1)*n) = (x^(-1))^n $\;$
Jan
26
revised Crypto library that supports ElGamal PET and Mixnets
improved grammar
Jan
26
answered Will current encryption always remain secure? Is there mathematical proof?