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Oct
5
comment Why do we require a CSPRNG's output to be indistinguishable from true random?
#2 is just as important, to me. Known shortcomings are obvious areas for analysts to attack, which they frequently do, and to devastating effect.
Oct
5
comment Why do we require a CSPRNG's output to be indistinguishable from true random?
"The only information the attacker can get from this is the cipher's block size, and this doesn't weaken the security one bit." [citation needed]
Oct
4
awarded  Yearling
Sep
21
comment If I know the hash function that produced a hash key, how easily can I generate an input to hash to the same key?
Also, your clarification about the difference between "any" and "particular" only confuses the issue more. You say by "any" you don't care what the string is, and then you say by "particular" that there may be several, but you don't care what the string is — both of those seem to be the exact same thing. Additionally, it's unclear what you mean by the word "convey".
Sep
21
comment If I know the hash function that produced a hash key, how easily can I generate an input to hash to the same key?
Keep in mind that if you know $k$ where $k = H(p)$ and $p$ is low entropy (for instance, the string hello), it is not considered difficult to find $p$.
Aug
28
comment Are there ANY text strings that will generate the same SHA-512 Hash output?
Good point. I've edited the answer to reflect that.
Aug
28
revised Are there ANY text strings that will generate the same SHA-512 Hash output?
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Aug
28
awarded  Nice Answer
Aug
28
revised Are there ANY text strings that will generate the same SHA-512 Hash output?
added 289 characters in body
Aug
28
answered Are there ANY text strings that will generate the same SHA-512 Hash output?
Aug
27
comment Ensuring integrity and confidentiality together with symmetric encryption
Integrity is in no way guaranteed by your protocol, unless you are using an authenticated mode. In many non-authenticated modes, depending on the particular use-case, confidentiality might not even be guaranteed (e.g., CBC and padding oracles). So yes, there is a problem with the given protocol.
Aug
24
comment Client login without sending a password
That said, you should almost certainly not attempt to implement SRP yourself.
Aug
20
comment Combining several symmetric ciphers using XOR
There is no indication whatsoever that they have. And if they have, the ability to do so is far too valuable to disclose by decrypting your data (unless you happen to be, say, Abu Bakr al-Baghdadi). Furthermore, the more you try to glue your own crypto together, the more likely it is for you to commit a mistake that weakens your overall security rather than strengthens it. Modern crypto is already the strongest weapon in our arsenal; it's infinitely more likely you'll get popped by using crappy passwords, poor op-sec, failing to update software, etc.
Aug
17
comment Is it possible to get an RSA encryption key by comparing the unencrypted and encrypted file?
One thing that you should consider is that in most real-world cryptosystems built on RSA, the public key of the recipient is explicitly included. So even if the "textbook" answer were "no", the answer in the real-world is almost assuredly "yes".
Aug
17
comment Is there a formal definition of what a distinguisher is?
The Wikipedia article on cryptographic advantage may be of use.
Aug
15
comment Hash and salt or salt and hash?
You should not be writing code to hash passwords yourself. Use bcrypt or scrypt and you won't have to care about details like these. Bindings are available for virtually any language you wish.
Aug
14
comment Is (AES-)GCM parallelizable?
Thanks for the correction! I've updated my answer to refer to yours.
Aug
14
revised Is (AES-)GCM parallelizable?
added 55 characters in body
Aug
13
comment Chopping off SHA256 entropy?
"More than one in a million" is probably really bad — especially because this number will grow very quickly as the size of data grows.
Aug
13
answered Is (AES-)GCM parallelizable?