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Security professional with many years of experience with the practical application of cryptographic algorithms and protocols. I'm helping with the design of protocols and API's within international standardization bodies. Lead developer of a common criteria certified product. Over 30 years of general experience with computers.

On crypto I mainly answer less mathematically inclined questions, leaving security proofs to the theoretical cryptographers and analysts.


Nov
12
comment How a file is encrypted?
Yes, reading them in an array is one option. For larger files binary streams and memory mapping may be more efficient though.
Nov
12
comment How a file is encrypted?
Modern crypto algorithms all operate on bits. Even PBKDF2 - which is used to derive keys from passwords - operates on bits instead of text. In modern crypto, the terms plaintext and ciphertext are rather confusing as neither one of them are actually text, you actually need character-encoding such as UTF-8 to convert from text to binary and encoding schemes such as base 64 to convert binary to text. So in that sense encrypting a file is actually easier as no encoding needs to be applied.
Nov
12
revised What is the use of segments in Cipher Feedback Mode (CFB)
added 23 characters in body
Nov
12
accepted What does OIW stand for
Nov
12
asked What is the use of segments in Cipher Feedback Mode (CFB)
Nov
11
revised Can RSA signing be implemented on top of RSA encryption/decryption?
added 95 characters in body
Nov
11
answered Can RSA signing be implemented on top of RSA encryption/decryption?
Nov
11
comment Handbook of Applied Cryptography as an entry point - is it ok book?
Sorry, the earlier. Forgot that somebody had the balls to name a book almost the same as Applied Crypto.
Nov
10
comment Handbook of Applied Cryptography as an entry point - is it ok book?
Personally I don't like Applied Crypto as an introductory course. It is more about understanding crypto than applying crypto. It's an important book in a historical perspective, but by now you would hope that there are better books available. Certainly from a developers point of view a book should cover more practical security than that it does. Problem is: I don't know a better book...
Nov
10
comment Are modified implementations of cryptographic algorithms a good idea?
You're welcome. Be glad that there are standardized building blocks to build your security on. Usually there is no need to change the blocks themselves. Sorry, probably the Lego movie talking :P
Nov
10
revised Are modified implementations of cryptographic algorithms a good idea?
added 522 characters in body
Nov
10
comment Does the SSH protocol preserve integrity if an endpoint is cloned?
OK, OK, as long as you can keep the session counter up to a certain point and you don't break the protocol then the MAC does not protect auto-magically against twin clients I suppose. But you would need the clients to both accept the same responses from the server even for different messages from the clients (deleting some old comments).
Nov
10
answered Are modified implementations of cryptographic algorithms a good idea?
Nov
9
comment Extending key sizes in Salsa20 and ChaCha?
I hope your code does contain whitespace. Why not create some paragraphs yourself next time around? That was barely readable.
Nov
9
revised Extending key sizes in Salsa20 and ChaCha?
added 4 characters in body
Nov
9
comment Which attacks are possible against raw/textbook RSA?
@DW I'll try and make sure Dan's survey is included in the CW answer though. I don't see the attack on session keys (with $m/2$ security) mentioned yet either.
Nov
9
comment Which attacks are possible against raw/textbook RSA?
@DW I (now) searched and found Dan's Survey. Padding is mentioned, but although it is claimed that he indicated that padding may thwart the attacks mentioned, he did not discuss it much. The main reason to ask is that I could not find too many specific (lists) of attacks that mentioned padding; I thought of creating a list myself, but as I'm not performing crypo analysis on a daily base myself, my list would certainly not be complete and possibly incorrect. There is much information about this but it is too much and too spread out.
Nov
7
revised Which attacks are possible against raw/textbook RSA?
3rd person
Nov
7
revised Is RSA encryption of a cryptographic hash with a private key the same as signature generation?
pointed to attacks on raw RSA - a question I posted as an extension of this Q/A
Nov
7
comment Crypto-Compression Algorithms?
This is also more or less the same point as this answer is trying to make, although your answer puts it a bit more clearly.