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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How to distribute session keys in public key cryptography?

In public key cryptography we can also use session keys which are symmetric. How do the sender (say a server) provides this session key information to its clients? If the sender (here server) ...
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Where is the proof of security of Diffie's cipher?

There is an apparently provably secure cipher that was proposed by Diffie, but enhanced by R.A. Rueppel. The scheme, which was mentioned in Applied Cryptography, works like this: Measure the length ...
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How can I make my cipher show the avalanche effect?

I am a beginner in cryptography. I designed an password based encryption-decryption algorithm, which uses a random salt and a password to encrypt a message. I'm using SHA-512 for hashing, matrix ...
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AES and perfect ciphers

I'm taking a crypto class this semester and after learning the definition of a perfect cipher. I started wondering how this definition applies to AES. Obviously AES isn't a perfect cipher, since the ...
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Verilog simulation of Data Encryption Standard

I interested in developing DES(in verilog) for my college project.Can i get help in understanding the simulation results of DES encryption and decryption ? thanks in advance .
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Using a Non-Random IV with modes other than CBC

The weakness CWE-329 is an interesting problem with CBC mode. However, does this same weakness affect the other modes of operation that rely upon an IV such as: PCBC, CFB and OFB? My gut feeling is, ...
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Does knowing common prefixes help crack blowfish?

I have strings that are if the form: {static data}{changing data} The beginning static data part is around 20 characters and is common to all strings. The last ...
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Trying to find a different DES encryption system explanation

I need a mathematical explanation of what does the DES encryption system really do. This means I need more explanation than the one that offers FIPS, which is more an explanation for computer ...
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Encryption technique performance evaluation

I've come up with a light weight bit wise encryption algorithm and seems good. Ive tried it with text and image input. But I've the following questions I would like to ask What do you think of bit ...
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101: Advanced Access Content System (AACS) and Subset Difference techniques for Broadcast Encryption

I'm trying to get a grasp on AACS and Subset Difference for a project I'm working on and am having a hard time coming up with a technically valid layman explanation, let alone implementation. Is it ...
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Avalanche effect in DES

I couldn't understand the avalanche effect in DES. Could someone explain how avalanche effect happens in DES
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Encrypting and obscuring data between site/user without SSL

Im trying to figure out what the best way to encrypt data sent between a webpage and the user(both ways) is, when hosted in an environment that doesn't support SSL. The purpose of encryption would be ...
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What is the purpose of four different secrets shared by client and server in SSL/TLS?

I was looking through the working of SSL V3, and found that a connection state is defined by a set of things, including client write mac secret, server write mac secret, server write key, client ...
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Can CBC ciphertext be decrypted if the key is known, but the IV not?

Let's say that there is a binary file encrypted with AES in CBC mode (i.e. using a key and initialization vector). If key is known, but IV is not, is it easy to fully decrypt the file? How hard is ...
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Why do we need special key-wrap algorithms?

Wikipedia says: Key Wrap constructions are a class of symmetric encryption algorithms designed to encapsulate (encrypt) cryptographic key material. We are using these algorithms to encrypt ...
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How does a key wrapping like RFC 3394 secure my cryptographic keys?

So I'm messing around in the BouncyCastle library with the RFC 3394 AES Key Wrap engine and I'm trying to understand the benefit of it. The problem I'm running into is how to store keys securely on a ...
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Is Blowfish strong enough for VPN encryption?

I'm looking at an OpenVPN connection between two sites configured to use 128 bit Blowfish in CBC mode, and trying to figure out how to assess the strength, but I just don't know enough of the maths. ...
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Decrypting DES with decrypted and encrypted data

I got two 8-byte strings. One which is decrypted is: FF FF FF FF FF FF FF FF and one which is encrypted is: ...
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If the PSK is known, is it possible to decrypt traffic from other clients in a WPA2 wlan network?

If in a public WLAN WPA2-PSK is used, but the PSK is more or less publicly available, does this mean that an attacker with that PSK can easily decrypt wlan traffic from/to other clients of that WLAN? ...
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451 views

Does the XML Encryption flaw affect SSL/TLS?

A "practical attack against XML's cipher block chaining (CBC) mode" has been demonstrated: XML Encryption Flaw Leaves Web Services Vulnerable. Does this weakness of CBC-mode which is used here also ...
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370 views

How can I encrypt more than 64 bit with the Data Encryption Standard?

The Data Encryption Algorithm is designed to encipher and decipher blocks of data consisting of 64 bits under control of a 56-bit key. If my data is more than 64 bits, (suppose 66 or 67 bits), will ...
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Is the CBC weakness in XML Encryption a new discovery? Are other applications vulnerable?

The RUB in Germany reports that XML encryption is broken. This is essentially the W3C standard for protecting XML documents from prying eyes. Does this mean that an attacker can only see a single ...
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Deniable Encryption from simple primitives

Is there a deniable encryption scheme $M = E(p_1,k_1,p_2,k_2,...,p_n,k_n), p_j = D(M,k_j)$ of $n$ plaintexts $p_1,p_2,...,p_n$ and $n$ keys $k_1,k_2,...,k_n$, such that we can fix $D$ to be a known ...
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Getting the encryption method and key from the encrypted data and the raw data

I have some pairs of plaintext and ciphertext data, from which I need to be able to decrypt the other passwords stored in the database. The password field typically contains something like ...
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How can I encrypt + authenticate short strings into similar short ciphertexts?

I wish to manipulate short ASCII strings (namely unpredictable domain names) into a form which cryptographically assures authenticity and confidentiality, for use in the local part of email addresses. ...
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How can I store confident data with OpenID?

I want to make a system that needs to store some confident user information in a database. I intend on using OpenID for user authentication. I would like encrypt the data in a way that it can only be ...
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AES in ECB mode weakness

In a project that I'm currently working on, we are encrypting some data using AES with ECB mode in a database. Each piece of data being encrypted is very small, no more than 10 characters long. Very ...
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When is an asymmetric scheme considered broken?

Does the following quote imply that valid encrypted data can be created and decrypted by someone other than the owner of a private key: An asymmetric encryption scheme is considered to be broken ...
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How common are SEED certificates outside of Korea? When is support required?

I'm looking at the SEED algorithm and would like to know if this is still in common usage. Can anyone tell me when I would need to implement this standard, either as a client or a server?
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How do other, non-RSA algorithms, compare to the PKCS #1 standard?

Arguably the PKCS suite of standards have a profit-oriented bias as they are promoted by RSA and promote their algorithms over others in the form of RFCs and other means. I'm considering the ...
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What is the likely cause the RSA algorithm gives back plain text in this case?

Text book question of Chapter 9 of "Crypto and Network Security" by William Stallings: When using the RSA Algorithm — if a small number of repeated encodings give back the plain text, what is the ...
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Encryption scheme for social-network-like data sharing data via untrusted server?

I am thinking quite a lot lately abut the problem of secure, privacy-preserving social networking. Distributing the network among trusted, preferably self-hosted servers (like Diaspora, GNU Social ...
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How does one scale encryption strength upwards from 256-bit?

I have seen many examples of encryption up to about 256-bit. But how does one programmatically scale the logic upwards in a language such as PHP or Java to say 1024-bit or even 4096-bit and higher? ...
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SIM security for two messages

Here SIM means the simulation based security Consider a two message encryption scheme:$$Enc:K \times M \times M \rightarrow C \times C$$ and $Enc(K, m, m')=(K \oplus m, K \oplus m')$, In ...
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Is there a secure cryptosystem that can be performed mentally?

I, myself, do not plan on getting into a situation where I would be unable to use a computer in order to communicate securely. However, I can think of many practical situations in which mental ...
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Is CBC really dead?

I developed a p2p-app in C# which sends and receives encrypted text messages (50KB). For encryption, my app uses AES 128 bit in CBC cipher mode. For each message it uses a new randomly-generated IV. ...
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What is the difference between a stream cipher and a one-time-pad?

A (synchronous) stream cipher is an algorithm which maps some fixed-length key to an arbitrary-length key-stream (i.e. a sequence of bits): $C : \{0,1\}^k \to \{0,1\}^{\infty}$. This key-stream is ...
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Where can I find Secp256k1 ECDSA test vectors?

I`m currently implementing an ECDSA library based on curves like secp256k1. I would like to test it using some test vectors, like ...
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Why isn't the IND-CCA property inherited when sending redundant ciphertext?

Suppose that in order to avoid loss in transmission, a secret key encryption scheme $(Gen, Enc, Dec)$ is modified to be $(Gen, Enc', Dec')$, such that the message m is encrypted independently ...
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Hashing or encrypting twice to increase security?

Over on the bitcoin forums I asked why the bitcoin client computes SHA-256(SHA-256(x)) as its cryptographic hash for a variety of purposes. The leading theory--since the bitcoin author has ...
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How to attack a classical cipher using known partial plaintext?

I have a ciphertext generated by a classical cipher. I do not know what was cipher used to generate it. I do however have the beginning of the plaintext. What are the cryptanalysis approaches for ...
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Is Convergent Encryption really secure?

Recently a company called Bitcasa demonstrated a product of cloud storage. they indicated that they would use "Convergent Encryption" to secure your data and de-duplicate, essentially one copy of the ...
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What causes first block of AES decryption to be garbled, even with correct IV?

I am attempting to duplicate wireshark's packet capture decryption for a TLS HTTP session, where I control the private key of the server. The cipher suite number is 0x00002f, TLS_RSA_AES_128_CBC_SHA ...
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What advantage does facebook's new encrypted access_token have?

When a user on facebook grants an app access to their account, an API key is issued to the app. This key is app and user-specific. This process is described in Facebook's developer documentation. ...
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Is modern encryption needlessly complicated?

RSA, DES, AES, etc. all use (relatively) complicated mathematics to encrypt some message with some key. For each of these methods, there have been several documented vulnerabilities found over the ...
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GPG symmetric encryption and javascript

I have a use case where I need to encrypt some text in the browser using javascript. Only the encrypted text will be stored on the server. The user should then be able to take the encrypted result and ...
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Is it safe to encrypt a public key alongside a message with AES?

If I have a message M and a public key P, and I encrypt them alongside one another: CIPHER = AES(M + P, aes_key) Is CIPHER now weakened if someone knows what P ...
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Are there public slow-but-strong algorithms out there that resist brute-force attacks better?

I'm reading that AES uses 4x4 bytes (4*4*8 = 256 bits key) matrix for performances matters (since it's a requirement for common standard encryption algorithms), but are there implementations with ...
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What is sent on the initial communication with Kerberos?

When a user wants to communicate with another user (let's say Alice and Bob), what is sent over the network during the initial communication? Alice uses her Kerberos client and enters her password ...
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Is public-key cryptography the only option in this scenario?

Two parties: a client and a server are to a agree on a symmetric key. Both the client and the server are aware of a master password. The way this is currently done ...