# All Questions

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### How to exchange authentication keys

I am trying to create a secure Bluetooth Low Energy connection. The peripheral server (the main device other people would connect to) would need to service many clients (users) and due to hardware ...
1k views

### ASCII to same-length ASCII encryption?

I need to encrypt an ASCII string [a-zA-Z0-9:] to an ASCII [a-zA-Z0-9] string of the same length. It doesn't have to be unbreakable, it's sufficient that it won't be readable at the first sight. The ...
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### System of linear congruence, not relatively prime [migrated]

Consider we have the following set of congruences $$x\equiv b_i \pmod {m_i}$$ for all $1\leq i\leq d$. $m_i$'s doesn't have to be relatively prime, so the Chinese remainder theorem doesn't work here. ...
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I'm pretty new to this and find it quite interesting, but my brain won't process how it works so I have to ask some questions :) Why is cryptography used? Is it for extra security once the password ...
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### Why cant Public Key Encryption be perfectly secure? [duplicate]

I would be very grateful for any help. I cant figure out why (probabilistic) public key encryption schemes can never provide perfect secrecy? Any Ideas? Excerpt: In contrast to the private-key ...
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### How to get the (x,y) from the EC point in the pubkey of an ECDSA certificate?

I have this certificate, and I have the bitstring of the pubkey that should represent Q = (x,y) = [d]P. How can I get the x part? (The curve is the NIST B-163)
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### Recovering key length from transposition block cipher ciphertext

First of all I would like to say hello to all StackExchange users. So far I've been stalking the forum for some time, now it's time to leave the shadows. In my master thesis I'm writing about ...
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### Outsourced Multiparty computation proof in Ideal world

I need to know in an outsourced two party computation where honst $A$ and $B$ outsource their private and secure data to a malicious server, why we need to design a simulator that interacts with an ...
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### Protocol for signing and timestamping documents for e-archive system [migrated]

we are building system for storing PDF file for long term in database. Before we store PDF file in database we have to: ...
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### Is there a tangible benefit in keeping the number of PBKDF iterations secret and not storing them with the ciphertext?

Suppose I have a local file and it is encrypted with a symmetric key derived from a strong passphrase, unique salt and $x$ number of PBKDF (e.g. Scrypt) iterations. I am interested in keeping this ...
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### Durability of the crypto container and there old copies / backups [closed]

Do durability of the crypto container decrease if I will store near that old copies of this container / backups? If yes, how much it falls? I feel that when I do backups it reduce resistance of ...
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### what is the public information in Elliptic curve cryptosystems [closed]

Currently my knowledge about Elliptic curve is quite limited to the textbook and I don't know how a practical Elliptic curve cryptosystem works. I read an example about key exchange using Elliptic ...
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### DH with AES - is that an acceptable security scheme over UPnP?

I'm trying to devise a good security scheme to protect comms over Wi-Fi. Right now, I have 2 devices that already communicate via UPnP but I need to secure this communication. I've come up with this: ...
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### Is HMAC-MD5 still secure for commitment or other common uses?

MD5 collisions have been out for some time. In spite of this, HMAC-MD5 is still secure for authenticating data1. This illustrates a strength of the HMAC construction, it does not require that the hash ...
57 views

### where should private and public keys be stored? [closed]

I am kind of confused whether should a newly generated key pair be stored in a keystore or in just a normal plain text file? From what I read from online source, there are serveral explainations ...
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### SHA3 Keccak, absorbing data to the state

I'm working on implementation of keccak algorithm and have one problem. Tell me please, takeing an example "test": will state (before block permutations, but after padding - pad10*1) look like this: ...
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### Second generator for secp256k1 curve

I want to get a group element $h$ on the elliptic curve secp256k1. The important thing is that no one should know the discrete logarithm of $h$ with respect to $g$. That is, $h$ should be created from ...
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### XOR = Best encryption? [duplicate]

If you have a TRULY random key (in binary) and you have a text (in binary) that you want to encrypt. Can you simple XOR the key and the text? Is that secure? How secure?

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