Top new questions this week:
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I have tried out an encryption method, in which I swap bits in the text.
The text length is N bit, then I generate several random number pairs in the range 0..N-1, as [n,k] pairs. After that I swap ...
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Why can't uncomputable functions be adapted to serve as theoretically perfect one-way functions? This has been bugging me for years, and I've never been able to track down an explanation of why it ...
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A malicious actor wants to decrypt ciphertext that was encrypted with a password. He also possesses the hash (bcrypt/PBKDF2) of that password. Does he have any significant practical advantage in ...
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I'd like to use the Itoh-Tsujii algorithm for a dynamic substitution table, but I do not get the following line:
$$r\ \gets\ (p^m - 1)\,/\,(p - 1)$$
And why can $r$ be used to calculate the ...
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After looking at this bitcoin-related ECIES repo I believe the intention is that, at least in some cases, the recipient would know that the message is intended for them and use an secp256k1 public key ...
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Usually the sort of trapdoors which are talked about are designed such as to make the computation intractable for one party and tractable for the other.
But what if one party merely has a big ...
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I think that I've found a good solution to prove the knowledge of an ECDSA signature without revealing it.
In short terms it consists in generating an ECDSA signature using the point $R$ as generator, ...
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Greatest hits from previous weeks:
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Would it be possible to create a program with which to create a cryptographic algorithm (i.e. encryption or hash) using well-known elements of other algorithms in the same way that algorithms "reuse" ...
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I think 1024 bit RSA keys were considered secure ~5 years ago, but I assume that's not true anymore. Can 2048 or 4096 keys still be relied upon, or have we gained too much computing power in the ...
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I am often told that any key can be broken and that it is only a matter of time and resources for any key to be broken. I know that this is technically true. However, I think that there is probably a ...
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A message may be accompanied with a digital signature, a MAC or a message hash, as a proof of some kind.
Which assurances does each primitive provide to the recipient?
What kind of keys are needed?
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For example, in RSA, we use this for encryption: $ciphertext = (m^e \mod n)$ and for decryption.
If our message is "hello world", then what number do we have to put as $m$ in the RSA formula?
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I have three questions:
Would you use HMAC-SHA1 or HMAC-SHA256 for message authentication?
How much HMAC-SHA256 is slower than HMAC-SHA1?
Are the security improvements of SHA256 (over SHA1) enough ...
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One runtime platform provides an API that supplies PKCS#5 padding for block cipher modes such as ECB and CBC. These modes have been defined for the triple DES, AES and Blowfish block ciphers. The ...
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Can you answer these questions?
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Just like in this question: Protocol for proof of knowledge of $l$-th root
I want to prove that for $u^e = w$ I know $u$ without revealing it.
Three other requirements are:
e is small (65537)
The ...
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A reasonable way to do password-based encryption is:
put the passphrase¹ and nonce in a well-parametrized memory-hard iterated hash function like Argon2, to derive a key 128-bit or larger.
output ...
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My question is a follow-up to a recent question regarding quantum-secure time-lock puzzles (TLPs). TLPs can be built (in principle) from indistinguishability obfuscation (iO) [BGJ+,BGL+] as noted in ...
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