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| bio | website | conradoplg.cryptoland.net |
|---|---|---|
| location | ||
| age | ||
| visits | member for | 1 year, 8 months |
| seen | 18 hours ago | |
| stats | profile views | 14 |
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Mar 6 |
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How are Elliptic Curve Cryptography and Pairing Based Cryptography related? Yes, but the only alternative I know is PBC using elliptic nets, which are related but different to ECC. |
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Feb 1 |
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Decryption a chunk of file with AES That's completely up to you. In your example, you have 10 chunks; you can decrypt the first five in one thread and the last five in another. The only restriction is that the size of each chunk must be a multiple of the block size of the cipher, e.g. 16 bytes in the case of AES. |
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Feb 1 |
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Decryption a chunk of file with AES Sorry, I'm not sure what is you question. Read the initial counter value. Determine the number of blocks, divide by the number of (e.g.) cores, and decrypt each chunk of blocks in each core. |
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Jan 25 |
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Modulus for elliptic curve point multiplication I strongly suggest you to refer to a stardard reference like Hankerson et. al's "Guide to Elliptic Curve Cryptography" or Menezes et. al's "Handbook of Applied Cryptography". Anyway, if the result of the subtraction is negative, simply add $p$ to the result (since you're working modulo $p$, this will not "change" the value). |
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Jan 22 |
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Modulus for elliptic curve point multiplication You can use any irreducible polynomial. Usually it's $x^2 + 1$, which is irreducible if $-1$ does not have a square root modulo $p$. The same for other degrees: use a $n$-degree irreducible polynomial. Note that for efficiency a "tower of extensions" is often used (e.g. quartic extension can be built as an quadratic over another quadratic). Ask another question if you need details. I also suggest reading this: everything2.com/user/Swap/writeups/finite+field |
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Sep 27 |
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why $e(g,g)^N=1$ in bilinear pairings holds? Yes, since $e(g^{a_1},g^{a_2})^N = e(g,g)^{N a_1 a_2} = (e(g,g)^N)^{a_1 a_2} = 1^{a_1 a_2} = 1$. |
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Sep 27 |
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why $e(g,g)^N=1$ in bilinear pairings holds? No, if the order of $g$ is the composite $N$, then $g^q$ and $g^p$ will be different than $1$. The reason that $e(g,g)^N = 1$ holds is that $e(g,g)$ is the generator of $\mathbb{G}_T$ and has order $N$. |
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May 4 |
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Elliptic curves for ECDSA You can find $n$ by factoring the order of the curve, which you have found with e.g. Schoof's algorithm. Then $n$ will be the largest factor, and $h$ is the order divided by $n$. |
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Feb 10 |
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Best choice of finite field for AES on a 4-bit microcontroller? @IlmariKaronen: I guess you're right. Thinking back, you can compute inverses in $GF(2^4)$ by simply trying all 15 possibilities. It seems that this issue warrants some research :) |
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Feb 9 |
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Best choice of finite field for AES on a 4-bit microcontroller? Using composite field arithmetic allows you to compute an inverse by computing a single inverse in $GF(2^4)$. It seems to me that the code required to compute this would itself be greater than 256 bytes, killing any advantage over using a precomputed S-box. But it's hard to say without actually implementing it. |
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Jan 26 |
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Helper data authentication in PUFs I guess my question wasn't clear enough, sorry for that! Suppose that the PUF is used by some device to derive a key that is used to encrypt and authenticate its hard drive, for example. There is no user interaction. If the device generates and stores a key to sign $P$, then an attacker can change both the key and $P$ (that is, assume that there is no secure storage) and the security would be compromised. If you assume there is a safe place to store the second key and $P$, then why use a PUF in the first place if you can generate a key and store it there? |
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Jan 24 |
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Helper data authentication in PUFs Thanks for the clarification, but I still don't understand something: how can I protect it against modification? For that I would need a key, but I'm using the PUF to get a key in the first place. Is there any kind of guarantee that an attacker can't change $P$ in such a way to force the system to derive a key $R'$ of his choice? |
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Jan 24 |
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Helper data authentication in PUFs I see, it makes sense if the PUF is used for authentication. But what if the PUF is used to generate a key for a device? |
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Jan 10 |
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Would it be secure to use random numbers from random.org in a cryptographic solution? One application I can come up with is for validating randomness tests. But for the usual applications (e.g. generating keys), I don't see how random.org could be useful. |
