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 Yearling
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Jan
12
comment References for cascade
In classical crypto, combining transposition and substitution processing is generally a good idea IMHO.
Jan
12
answered Efficient AES - Use of T-tables
Jan
9
comment What are the main weaknesses of a Playfair cipher, if any?
Merely a side comment: The weakness of Playfair as pointed out in the answers could be somewhat compensated by combining Playfair with transpositions, e.g. columnar transpositions.
Jan
6
comment NIST tests for AES
@RichieFrame: What is in Appendix C of FIPS 197 is simply known results of certain test vectors. Hence it is a simple comparison to be done by the implementor. What is in AVS is however very much more comprehensive and requires some coding to be written carefully.
Jan
5
comment NIST tests for AES
Sec. 6.1 of the document says: "To initiate the validation process of the AESAVS, a vendor submits an application to an accredited laboratory requesting the validation of their implementation of the algorithm specified in FIPS 197 ...". This means IMHO that an officially trusted laboratory is to (independently) certify the correctness of an implementation. If the implementer himself writes such a test suite there wouldn't be independence and the result would remain uncertain. (Analogy: In normal programming one could write one's own test codes but often risks to oversee one's own mistakes.)
Jan
5
comment NIST tests for AES
Standard conformity test of AES implementations can be easily done according to Appendix C of FIPS-197. In case you have problems with that, you could compare with my Python coding of AES (s13.zetaboards.com/Crypto/topic/7385224/1/) where the test is performed with the function checkencryptionwithfips197().
Jan
2
comment When/why is RSA (hybrid) encryption used rather than alternatives?
@fgrieu: I completely agree with you. But I merely called attention to the fact that not all applications require extremely high processing speeds. Anyway I interpreted the title of samoz's OP to mean that he desired some simple convenient way to encrypt certain arbitrary long personal messages with RSA alone. In that case, even with an interpreted language like Python, my own coding experience is that cpu time of the order of 1 sec is easily achievable.
Dec
30
comment When/why is RSA (hybrid) encryption used rather than alternatives?
In contrast to your 1st paragraph, I deem desiderata of the genre of the title line of samoz's thread to be principally justified from the perspective of software engineering. For, if a software depends on more than one algorithm (i.e. hybrid schemes), then one would have troubles, if one of the algorithms happens later to encounter security problems, while, if it depnends only on a single algorithm, the number of worries in the life cycle of the software is anyway minimized. Overall, I consider processing efficiency less important than simplicity and ease of understanding and maintenance.
Dec
29
comment When/why is RSA (hybrid) encryption used rather than alternatives?
Required speed of processing is IMHO highly dependent on the applications. In the case of personal messages between common people I wonder whether a cpu time of the order of 1 sec would ever be inacceptable. I am not sure (due to my humble knowledge), but I surmise that the article weakdh.org/imperfect-forward-security.pdf could eventually be of some interest to you.
Dec
28
comment How can I use asymmetric encryption, such as RSA, to encrypt an arbitrary length of plaintext?
Unfortunately owing to my insufficient explanation, an earlier post of mine is unavailable to you. You can find however in Example 3 in the Appendix in s13.zetaboards.com/Crypto/topic/7234475/1 an encryption of a plaintext of arbitrary length in the sense of the common block encryption, i.e. exactly what you asked.
Dec
12
comment Historic Authentication Schemes Before Computers
There were very old historical cases in China where secret or important messages were carried by couriers. A certain sentence or pattern was drawn on a piece of wood which was then separated into two halves and securely kept by the communication partners. When a messenger came with a piece that matched the other half, he and hence the message was considered authentic.
Dec
4
comment What is cryptographic agility?
I don't know, but there is anyway the term "key agility", see schneier.com/paper-aes-agility.pdf
Dec
2
comment Now that quantum computers have been out for a while, has RSA been cracked?
There are arguments claiming that quantum computers would have unrealistically huge power-consumption for achieving the same error rates as today's classical computers. (I cited a reference to that together with other citations on the possibility of realization of quantum computers in a post of mine s13.zetaboards.com/Crypto/topic/7457176/1 )
Nov
24
awarded  Yearling
Nov
24
asked What followed findings of A. Lenstra et al. concerning shared factors of practical RSA moduli?
Nov
5
answered Which method to generate one time password?
Nov
5
answered Is there an algorithm to hide text in another text, while preserving the meaning of the latter?
Oct
26
answered How were semagrams encrypted in the pre-digital era?
Oct
18
comment How are primes generated for RSA?
@Vilx: You are right. I was rather directly commenting on the post of mikeazo above, which, I presume, somehow answered your OP.
Oct
16
answered How are primes generated for RSA?