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.

learn more… | top users | synonyms

1
vote
1answer
92 views

How do we arrive to the equation for solving D in RSA?

We have been shown that DE is congruent to 1 mod phi(n). How do we arrive to the real equation for figuring out d that is d = e^-1 mod phi(n). I want to know the entire process. I am just curious, ...
1
vote
2answers
227 views

Shamir's Simple Sharing Scheme - preventing partial recovery of data

In SSSS, if you recreate the original secret with one of the decoder inputs being slightly damaged (e.g. one or two chars incorrect), you receive a slightly damaged version of the original secret. So ...
1
vote
2answers
215 views

Why can we always assume that $Gen$ algorithm choose key uniformly?

Talking about a (symmetric) encryption scheme $\Pi=(Gen,Enc,Dec)$ where $Gen$ take the security parameter $n$ as input and generates a key $k$ of length $n$. Generally speaking we say that $Gen$ ...
1
vote
1answer
2k views

What does AES256-CTS-HMAC-SHA1-96 mean in relation to Kerberos?

I'm not completely clueless as to what it means, but I'd like to understand it at a higher level. The highest encryption type used by Active Directory domain controllers for Kerberos authentication ...
1
vote
2answers
120 views

PPT eavesdroper able to output $m_{0}$ and $m_{1}$ of different lengths

I've read the following two questions and their answers: Messages of different lengths and one-time computationally-secret Why is a non fixed-length encryption scheme worse than a fixed-length one? ...
1
vote
1answer
240 views

Encryption schemes and pseudorandom permutations

Can an encryption scheme (deterministic or not) be viewed as a pseudorandom permutation taking as input a message and returning a value of the same bit-encoding length ? Thank you.
1
vote
1answer
559 views

Sending TLS messages with out encryption using openssl code

Is it possible to send messages over TLS with out encryption? If so which cipher suite is needed for this?
1
vote
1answer
118 views

How can I split a message in parts of similar size or smaller?

I have a 130-160 characters message that I need to split in say, 3 parts, and be able to reconstruct it by recovering all 3 parts. I also need that these parts are type-able, meaning that they can't ...
1
vote
1answer
260 views

Security of Salsa20 with some known plaintext?

Basic question- if I'm encoding a bunch of known filetypes with salsa20, will it still be secure if the plaintext header is known? Assume that a different IV and Key are generated before each file is ...
1
vote
1answer
125 views

In which disciplinary category can cryptography be put?

Is it a multi-disciplinary, inter-disciplinary, cross-disciplinary, or maybe even trans-disciplinary? What are the basis to describe each kind? I mean, how can we infer by which disciplinary field we ...
1
vote
4answers
289 views

Bad/Crackable Encryption Example?

I've been tasked with building up some security exercises (basic CTF training kind of stuff) for work. This should contain a bit of crypto, but my knowledge in this space has been limited to using the ...
1
vote
3answers
1k views

How to check the strength of an encryption algorithm?

I asking for advice on how to check strength of an encryption algorithm.
1
vote
1answer
3k views

How do I derive the time complexity of encryption and decryption based on modular arithmetic?

I want to calculate the time complexity of two encryption and decryption algorithms. The first one (RSA-like) has the encryption $$ C := M^e \bmod N $$ and decryption $$ M_P := C^d \bmod N. $$ ...
1
vote
1answer
789 views

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. ...
1
vote
1answer
1k views

How can 3DES encryption use decryption in the middle step?

I have been reading about the 3DES algorithm and I cannot understand one part. In 3DES we do following operation: $$C=E[K_3,D[K_2,E[K_1,P]]].$$ Where $C$ is ciphertext, $P$ is plaintext, $E$ is DES ...
1
vote
2answers
93 views

Encrypting documents through a proxy key

Suppose I'm developing an app to secure a lot of documents. These documents were encrypted (say, using AES) with a key X. This key X is basically the password that the user enters before wanting to ...
1
vote
1answer
169 views

ID-Secret Scheme

I have an ID-Secret scheme and I'd like to hear if there are any vulnerabilities present. Party 1 and Party 2 hold some credentials, an ID and a Secret. Party 1 Creates this message: ...
1
vote
2answers
112 views

How can a cryptosystem be unconditional secure?

How can a cryptosystem be unconditional secure ? The definition of an unconditional secure cryptosystem states that the cryptosystem cannot be broken even with infinitely computational ressources ...
1
vote
2answers
63 views

Using bcrypt derived keys for encryption?

Sorry for this ignorant question but I am currently weighing up the advantages and disadvantages of BCrypt over PBKDF2 and from what I have read BCrypt is considered more secure but from what I have ...
1
vote
1answer
146 views

How can a good pseudo-random number generator be made?

I am trying to make a pseudo-random number generator so that I can use it in a synchronous stream cipher for encrypting plain text. I want it to generate numbers which are as random as possible. What ...
1
vote
1answer
126 views

Why does openssl use SHA1 in ECC when I use secp384r1 curve

I need a small clarification that why openssl using SHA1 in ECC when I am using secp384r1 curve, but in rfc they are saying we should use SHA2. Thing here is am using nanoECC in my DTLS, nanoECC ...
1
vote
2answers
133 views

Operation which needs much computing power to be created, but just a little to be solved?

Does somebody know a cryptographic/mathematic operation, that needs much computing power to be "encrypted"/"created" but doesn't need much power to be "decrypted"/"solved"?
1
vote
1answer
64 views

How to encrypt letters less than block n using Hill Cipher

I am learning about Hill Cipher and know that it is a block cipher where each block of n letters (considered as an $n$-component vector) is multiplied by an invertible $n \times n$ matrix, again ...
1
vote
2answers
135 views

Random vs. Fixed Paddings

Is there any consensus (i.e. are there any research results) on the benefits and drawbacks of various padding schemes? Generally there seem to be two kinds of them: random paddings, like ISO10126 ...
1
vote
1answer
133 views

DES Encryption Algorithm all 64 bits for key instead of 56 bits

Would a DES algorithm that uses all 64 bits for the key instead of just the 56 bits be more secure? I have been thinking about it but those 8 bits used for parity are very useful and but including ...
1
vote
1answer
51 views

Data I/O operations for encrypted files

I need to implement a simple approach on a Linux system to encrypt/decrypt data and I would appreciate any feedback from you. Basically, I need to change a bit the behavior of the functions ...
1
vote
1answer
110 views

Rate my idea: is that a stronger GPG-like algorithm?

I came up with a simple idea but I don't know if it is really secure or not. I know that you shouldn't create any algorithm on your own. I'm just curious, that's all. Algorithm explanation: First ...
1
vote
3answers
102 views

Encryption time in ECC

In RSA, encryption time is usually much less than decryption time due to having a small public exponent. Can this be achieved in Elliptic Curve Crypto (ECC)?
1
vote
2answers
131 views

How to retrieve the plaintext of a substitution ciphertext?

So the other day, I was piqued by a ciphertext that was trivially encoded through substitution. Solvable only because we can use our eyes to determine word boundary word detection, etc. Trawling the ...
1
vote
1answer
63 views

Using beginning of TLS ecnrypted data to reveal secret [duplicate]

I have the following question about TLS security: Assume TLS-PSK protected HTTP with AES256-CBC cipher. When a TLS connection is established, client sends some encrypted data, where the plaintext is ...
1
vote
1answer
169 views

Derive both MAC and AES keys from same PBKDF2?

When doing password-based encryption, is it OK to create one instance of PBKDF2 from the password, and then use it to create both the AES key and the MAC key? (Or should a new instance of PBKDF2 be ...
1
vote
1answer
187 views

Short length asymmetric encryption?

I want to send out short messages to the world which listeners could verify to be send from me. The way this is usually done is to encrypt the message with a private key where the readers decrypt it ...
1
vote
1answer
66 views

PRP representation size

I'm now studying the block cipher substitution-permutation network construction and realized that it uses several small pseudo-random permutations instead a big one for saving memory (or that is one ...
1
vote
1answer
224 views

randomly generated key reused with XOR

If I have a long randomly generated key (k), XORed with a message (m), but since the message is longer than the key, there is a chance of reusing the keystream with the same message, but the key is ...
1
vote
1answer
388 views

What's the difference between the long term key and the session keys?

I'm currently studying secret key cryptography, and I've come across the terms "long-term key" and "session key". What's the difference between these two kinds of keys?
1
vote
3answers
229 views

Encoding numbers that can be decoded mentally?

I have a lot of objects, all of which need a particular number tagged on them so I can quickly tell the customer accordingly. But the problem is that the customer should not know what these numbers ...
1
vote
2answers
210 views

Re-using parts of a one time pad to encrypt a new one?

The main problem with OTP's is the fact that they can only be used once. Would it be possible to use a random number that's, say, 512 digits, then use 256 of those for the (non-random) message, the ...
1
vote
1answer
157 views

Which keys are necessary to decrypt Application data in a SSL connection?

I'm debugging an application which communicates between client and server using a SSL/TLS connection, and want to capture and analyze the sent data. Are the client write keys and server write keys ...
1
vote
1answer
192 views

ECKS-PS algorithm: searching in encrypted data; bilinear maps

I have found an encryption algorithm named ECKS-PS (published in the paper Efficient conjunctive keyword search on encrypted data storage system) that allows an user to search in encrypted data. All ...
1
vote
2answers
172 views

Is such a crypto-system available?

$E(k_1, pt) = c_1, E(k_2, c_1) = c_2, D(k_{new}, c_2) = pt$, where $k_{new} = f(k_1, k_2).$ Sharing $k_{new}$ and $k_2$ should reveal no information about $k_1$. Clarifications: Being able to ...
1
vote
1answer
2k views

How can I implement the “Multiplication Modulo” and “Addition Modulo” operations in IDEA?

I am currently working on IDEA (International Data Encryption Algorithm), and I don't know how to perform Multiplication Modulo and Addition Modulo. This is how IDEA operates: IDEA operates on ...
1
vote
1answer
234 views

Digital Certificate Chain Verification

Does a certificate contain the complete chain of all certificates up to the trusted root certificate, or does the program that verifies certificates have to fetch each parent certificate individually ...
1
vote
1answer
118 views

Tips on conceiving safe software messaging platform

I have a personal project in mind in which I plan to use cryptography in order to let the users be confident in the fact that, even if all data get's stolen, it would be virtually impossible to crack ...
1
vote
1answer
619 views

iSeries (AS/400) Database File: password encryption

I am helping with a project in which an old software system on an iSeries is having a brand new .NET UI applied to it. It's going well... except... In order to allow users to login and maintain ...
1
vote
1answer
13 views

Does a cryptosystem provides unconditional security if and only if it provides perfect secrecy?

Is unconditional security and perfect secrecy one and the same thing, i.e a cryptosystem provides unconditional security if and only if it provides perfect secrecy ? I've wondered about the above and ...
1
vote
1answer
49 views

Perfect secrecy of a crypto system

Suppose we have the following crypto system: $P = C = K = \{0, 1, . . . , n − 1\}$, $E_k(x) = (x + k) \bmod n$ and $D_k(y) = (y − k) \bmod n$. Prove that the crytosystem has perfect secrecy. Perfect ...
1
vote
1answer
58 views

What Java actually stores inside Keystore when generating Keys?

When we use Keytool to generate a Keystore to store Private/Public keys, what Java actually stores inside the Keystore file ? I ...
1
vote
1answer
44 views

Key derivation for AES-Encryption key and HMAC

Okay so I have two options for how I would derive two keys for AES encryption and HMAC they are as follows: Run BCrypt on a users passphrase and then use the bouncy castle implementation of HKDF in ...
1
vote
1answer
68 views

Show that the equal difference property exits for a modified DES encryption system

My cryptology professor gave us this problem on a past homework assignment and I only managed to get one of the 3 parts correct. Needless to say, I want to know how to do the other two parts as well. ...
1
vote
1answer
64 views

Are there any many to one encryption frameworks available?

I am reasonably new to the cryptography. For my use-case I need a method where in I would need a receiver to accept encrypted messages from a range of senders (each having their own, say, public key). ...