Encryption is the process of transforming plaintext using a cipher into ciphertext to make it unreadable to anyone except those possessing the key. Decryption is the process of transforming that ciphertext back into plaintext, using the key.

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Does encryption of data/information take place in peer to peer networks like Gnutella, Bittorrent?

Do peer to peer networks like Gnutella, Bittorrent have any encryption system to secure the users privacy or encrypt the file/data being shared? Elaborate please.
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Highest prime factor that is Safe for a particular scheme

My question is how many bits of prime number is secure so that it cannot be factored from very large number? Until today how large prime factor is found in large number? Quantum computing find ...
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Time taken for a brute force attack on a key size of 64-bits

You can do $2^{30}$ encryptions per second and the key size is 64 bits. $2^{64}/2^{30}$ should give me the time taken for a brute force attack? What if you double the key size? How can I calculate ...
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A block cipher whose key changes after each block

I have been reading about various block cipher modes of operation, and all of them seem to treat the block cipher (including it's key and key schedule) as a sort of immutable black box. I would like ...
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Encryption with two meanings without computer or programming

Can one create a cipher with two meanings? Not two layers, two phrases in the same cipher in the way that it would have a meaning X, for example, if deciphered using Transposition cipher and meaning Y ...
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506 views

Should AES.decrypt(ct, wrong_key) return blank or wrong result?

I am trying to use AES as cipher for an application I am building. I am using a JavaScript library (https://code.google.com/p/crypto-js/) to perform encryption and decryption with AES. When I ...
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Proof that a hash matches an encrypted file

Assume that Alice has a file $F$ which she is going to send, in encrypted form to Bob. Alice possesses $F$ and an encryption key $K$. She sends to Bob the encryption of $F$ using $K$, $E(F,K)$ as ...
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Is it safe to use cipher block sizing instead of padding?

I'm using this kind of technique instead of padding of cipher buffer (here goes pseudo-code): ...
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Construct IND-CPA secure encryption scheme by combining two given schemes

I have two encryption schemes $\Pi_0, \Pi_1$, at least one of them is IND-CPA secure but I don't know which one. The task is to construct a scheme $\Pi$ that is guaranteed to be CPA secure and to ...
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Are parts of a pseudorandom string also a pseudorandom string?

I am working on an exercise that encrypts a message using only the first $n$ bits of a pseudorandom generator's output $G(k)$, i.e. $F_k(m) := G(k)_{0...n−1} \oplus m$. $k$ is chosen uniformly at ...
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Is there a way to do single key-pair asymmetric encryption?

All of the information on asymmetric encryption I can find uses key-exchanging to get a mutual symmetric key. What I am trying to do is encrypt a message with a public key and have it only readable ...
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How can you produce visual cryptography?

I would like to be able to "code" images such as the one seen here on Wikipedia. Is this generally produced with software, or does this require complex programming? Ideally, I would love to be able ...
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What exactly does a key do?

I am getting to grips with cryptography as a total newbie, and am struggling with encryption "keys" and how to visualize them. From http://computer.howstuffworks.com/encryption.htm/printable: ...
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Is that possible to use encryption higher than 256-bit?

When browsing websites with Chrome sometimes I can see a green lock and encryption info inside. It says the connection with this website is 128-bit or 256-bit encrypted with TLS1.2. So I'm wondering ...
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How is LUKS dm-crypt secure if the key is stored with the encrypted data?

I've posted this question over at superuser, but haven't had any success at getting answers. That's why I've posted it here. Furthermore, I believe this is a more appropriate place for it as it is ...
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One-time pad mistake in the transmission?

I have a question which arised by analyzing the one-time pad cipher. I encrypt a binary sequence $a_1,a_2,..,a_N$ using a one-time pad with key sequence $k_1,k_2,k_3,...$, so I send $a_1+k_1, a_2+k_2,\...
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521 views

How does the IV or initial counter increase internally for each block in AES CTR mode?

I am working on Intel AES-NI library and since the AES function is coded using low-level assembly instructions. I could not see how the IV or initial counter increases in CTR mode. In general, how ...
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What is the limit of plaintext required to break the Vigenère encryption?

A theoretical question about the Vigenère cipher: Without any knowledge about the key (not even it's length) can we tell how much known or chosen plaintext is needed for the adversary to completely ...
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How does redundancy in a file effects performance and security of encryption?

Does redundancy in a file or data effect performance and security of encryption? (for example for AES, if not for general case) Is it easier to encrypt something that has high redundancy or something ...
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Encrypted counter as IV in CBC mode encryption using same key

I'm currently working with a secure transport protocol that defines the IV to be a counter (incremental nonce) to be encrypted with the same key. This is a followup to a protocol that did not provide ...
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Encrypt a single file, chunk-by-chunk, each chunk using different key (AES)

Encrypt a single file, chunk-by-chunk, each chunk using different key. I am a security newbie (only took 2 security courses before) But currently I am using this encryption method for my Android ...
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Hashing a password with the password?

I was wondering if hashing a password with the password would be a good way of encrypting the password. So, the user must know his/her password to get the same result as the one in the database. Also, ...
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Is there an advantage to storing keys split between several hashes?

I have a question about the way to store a key or password that was used for encryption, so that the application can check if the user put in the right key for decryption. If I make a mistake, please ...
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AES CCM vs CCMP

Are the terms AES CCM and AES CCMP are equivalent, or is there any technical differences between the two?
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AES GCM implementation in c#

I am implementing an AES cipher in GCM mode in c# and have a few questions. My code is based on the code found here for reference. I'll copy in the relevant portions. http://blogs.msdn.com/b/shawnfa/...
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Why does 3DES need private key to decrypt?

I create two files, my.cer and my.pem ( include certificate and private key), I encrypt a file with my.cer, I use openssl smime -encrypt command. When decrypting data, it needs my.pem. I think 3DES ...
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What would currently make the strongest https connection?

when you look at the encryption websites use you will see that there is alot of diversity, some use 256 bit keys some do not, some use DHE-RSA some ECDHE some use sha 256 some sha1, but my question is,...
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Need help understanding this exercise's solution

We were given this exercise, which asks us to identify the types of keys used on this diagram: The solution was Kxa -> A's private key Kya -> A's public key KxB -> B's private key My question ...
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Combining secure hashes with insecure hashes?

Assuming I'm a bank which seeks for secure hash functions to use in the process of signing on digital contents. I'd like to explain / prove why using each one of the following hash functions might ...
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Why are MACs not included when defining Protocols?

I see often in literature related to cryptographic protocols that MACs (Message Authentication Codes) are not included in protocol definitions. For example: ...
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What are the pros and cons of SIP media encryption types SRTP, ZRTP, and DTLS?

I'm just getting used to SIP for my first time using Linphone. Which encryption is better and why? My Settings > Network > Media Encryption has the options of SRTP, ZRTP, and DTLS.
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Is RSA encryption without padding secure with NIST Key Establishment schemes?

NIST SP800-56B standard (addressing IFC-based Key Establishment schemes) defines some key establishment (KE) schemes using the RSASVE primitive in which the common secret $Z$ is encrypted with RSA-EP ...
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What information should I send along with an AES ciphertext and is there any standard to do that?

While using some crypto implementations I got to see that many times a comment is added to the ciphertext. For example: ...
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Double randomised HMAC verification to prevent timing attack

A way to prevent timing attacks for hash string comparison is to perform additional HMAC signing in order to randomize the verification process (see Double HMAC Verification). In addition to the ...
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Re-sending captured encrypted data

Let’s assume Bob is some algorithmic stock trading machine. Bob takes commands from Alice, who sends messages to Bob. For example: Alice could be sending a message to Bob to stop trading. But if ...
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Encrypt a message with hash function, shared symmetric key, but no cipher

I am very new to Crypto and need some clarification or input. The question is: Suppose that Alice wants to encrypt a message for Bob, where the message consists of three plaintext blocks, $P_0$, $...
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Determine AES key given encrypted and unencrypted files

Given an encrypted file, the original unencrypted (cleartext) file, and knowledge of which AES encryption algorithm was used, is it possible to determine the key that was used to encrypt the data in a ...
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Coding of unsigned int to prevent guessing next ID

Suppose we are assigning records an unsigned integer ID from a N-bit space (say 32-bit) in a sequential manner. Is there a way we can code this ID before showing it to the public such that someone can'...
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Why can't you just clone encrypted data and use it?

Let's take a contactless card for example (one for public transport lets say (i.e. MiCard)), the data is encrypted on the card and encrypted on the reader as far as I know. So how come somebody who ...
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Encryption for a short packet size

I have an 8051 microcontroller with a radio that can send packets with up to 32 bytes and I want to have the messages encrypted. It is a sensor network so I really only want to send one packet per ...
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How many of primitive point on the elliptic curve?

In elliptic curves for cryptography, I know $nG=O$, where $G$ is a base point represented by $G=(x_g,y_g)\ on\ E(F_P)$, where $n$ is Order of point $G$. For example, $P(0,6)$ is a primitive point on ...
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Ballot box with multiple parties. All can read it, or none can read it

I am trying to create a decentralized moderation system for the game Diplomacy, a game for seven players. In each round of a face-to-face game, each player writes their moves on paper then puts it in ...
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Can I decrypt the message having it encrypted with different keys?

I have some encrypted binary data I want to decrypt. I know nothing about it, but I can get it encrypted with as many different (random, unknown) symmetric keys as I want. The keys are long enough to ...
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When is it safe to not use authenticated encryption?

I have read the post Why should I use Authenticated Encryption instead of just encryption? When is it safe to not use authenticated encryption? I assumed hard drive volume encryption or per file ...
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Encrypting a short phrase into two keys. both with length of 32letters

It doesn't need to be crazy secure. I wanted to figure out if there's a popular practice when encrypting a short phrase (less than 32 letter long) into two keys (two strings 32 length). Doesn't need ...
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Diffie-Hellman for Encryption

In learning how DH works for cryptography applications, I'm coming across some confusing language. For starters, most of the time DH is discussed in the context of "generating" their shared secret. ...
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AES block cipher modes of operation

have a project in which I have to implement an en/de-cryption structure using a standard AES block of 128-bits in VHDL and I think I'm a bit confused. So I'd like to ask some questions about AES and ...
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How would I make a secret notation alphabet more secure?

Disclaimer: I was looking for a place to ask this question on SE and this site seems to be the most fitting. If this question doesn't belong here, feel free to redirect me. Just out of boredom and ...
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What is U2FsdGVkX1?

Using CryptoJS 3.1 I noticed that using 3Des, the encrypted message always start with U2FsdGVkX1 Why is the first part of the encryption always the same? What information does this hold and ...
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How to compute the dot product on encrypted values?

Is there a practical homomorphic encryption scheme that can give reasonable execution time results in computing a dot product: $$a_1*b_1 + a_2*b_2 +a_3*b_3 +\ldots+ a_n*b_n$$ I imagine the scheme will ...