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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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Which cipher text is easiest to guess the plaintext?

I know that there are approximately 2^88 diff erent permutations of 26 characters. The stream cipher A5/1, which generates a binary keystream using three irregularly clocked LFSR, and has a 64-bit key....
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2answers
40 views

Practical perfect security in bitwise XOR vs integer addition/subtraction cipher

XOR already provides perfect security in theory but it's hard to apply it in practice due to strict requirements. I was thinking about whether simple addition/subtraction in integer format would not ...
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0answers
18 views

How to Securely Transmit Salt and IV vector

Hello I wanted to ask something about my scheme. As we know, salt is being used to prevent rainbow attacks. In my scheme, in order to let the receiver to decrypt some data,generated one time to be ...
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0answers
21 views

Example of an attack on a message exchange which uses the homomorphic property

Can someone give me an example of an attack on a message exchange using this encryption scheme, that uses the homomorphic property? Note: It is not a homework question.
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0answers
31 views

encrypt data without a key, length stays the same, result differs each time? [on hold]

I am attempting to solve my friends encryption algorithm, however I have yet to even believe such a thing is possible: Rules: the cipher must result in the same length, the encryption process does ...
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1answer
47 views

Triple Data Encryption Standard

Based on this, it looks like something slightly wrong. What would need to be adjusted at the transmitter side to allow the receiver to decrypt the message/data?
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2answers
33 views

How to provide partial confidentiality and full integrity for a protocol message?

I want to provide confidentiality and integrity for a protocol. I don't want to encrypt the entire protocol message. I do not want to encrypt the header and timestamp of the protocol message, but I ...
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1answer
32 views

How do i manage encryption keys with a cloud provider?

I would like to provision services from a Software as a Service (SaaS) provider. This is multitenant environment (multiple companies will be using a single instance of the application, with a single ...
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0answers
54 views

Need help decrypting, very complex [on hold]

So I received a message from a friend that said "21 E5 B2 C6 04 90 C8 51 E0 5C 2D B4 3C 47 B9 0D AB E3 FF B6 5E 88 45 8B" and I was told it has 4 layers of encryption. The first is to convert ...
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1answer
30 views

Trivial Broadcast Encryption Scheme for video conferencing how well does it handle users joining or leaving a call?

Consider the trivial Broadcast Encryption Scheme for video conferencing, where each user shares a long-lived key with the broadcaster, and the session key used to encrypt a multicast message (or ...
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0answers
4 views

Hadoop Transparent Data Encryption: protection from interference of EDEK, EZK and DEK [migrated]

I am preparing a response to a security auditor. They have presented a generic question about the protection from substitution of KEK and DEK in a "normal" encryption mechanism. What protection ...
0
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2answers
35 views

Good Diffie Hellman Encryption Method

I've just made my own implementation of Diffie Hellman in nodejs (its for a project of mine). However the shared keys are integers, I want to use those integers as a key to encrypt data. This is an ...
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2answers
67 views

Encryption using static AES256 symmetric key vs ephemeral session key

For a hackathon I am designing an information exchange system for healthcare. Healthcare data is stored on unsecured systems. I want to assure confidentiality, integrity and authenticity of this data ...
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1answer
69 views

Avoid decrypting every password in a password manager

The Setup I'm making a password manager for fun. It stores a random encryption key, encrypted with a key derived from the master password, and then it stores the data, which is a list of (site, ...
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0answers
21 views

Which Approach is Better in Pseudorandomness - Asymptotic or Concrete? [on hold]

When to prefer these 2 approaches over each other and which one is more secure.
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1answer
64 views

Proving impossibility for a stronger primitive

I have a primitive $A$ which is impossible to prove under some hardness assumption in a black-box way. Now, if another primitive $B$ is stronger than $A$ - in other words $B$ implies $A$ - will it ...
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1answer
32 views

Ring Signatures: Why is the combination function easy to solve?

I'm reading Rivest's How To Leak A Secret and am on the part where they describe their signature scheme ("Generating a ring signature"). Why is computing $C_{k, v}(y_1, ..., y_r) = v$ easy? The ...
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1answer
33 views

Concept of hashing a group of data and validating if a value exists within the group

When learning about cryptography and hashing, I remember seeing a concept where you could hash a number of values (ID's for example) and then validate against the hash, not storing the original IDs. ...
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0answers
30 views

Want to know which encrypting algorithm shall I go for the wired connection RS485 the device has 52Mb memory

I have embedded Linux device in which total memory I have is 52MB. This device is distributed system in which 100 nodes can connect each other in wired connection using RS485 as master and slave ...
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2answers
264 views

Is it safe to use a timestamp to build a nonce?

I'm writing an application, which can be used on multiple clients, and share data on a server. To make sure the data never leaves the clients unencrypted, the application should offer encryption with ...
1
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2answers
115 views

Append text to file without decrypting & encrypting again

Is it possible to add a line to a file which is encrypted symmetrically or asymmetrically (private key refers to readkey below, public key refers to append key then) without decrypting it? I was ...
0
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1answer
34 views

AES-GCM conformance test

Is there any conformance tests/sequences to validate AES-GCM & GHASH() implementation? Details: I'm implementing AES-GSM, that's just for better understanding of that stuff, nothing more. Well I ...
3
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1answer
51 views

How do applications set up secure communications through an untrusted middleman?

I recently discovered Tox whilst looking for alternatives to Skype, and while the Tech FAQ goes into some details about algorithms used, etc. I don't understand how keys are securely exchanged. I ...
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1answer
29 views

Hybrid encryption for MQTT payload?

i've written a simple code for payload encryption, i'v done it with AES-128 CBC mode ,it works fine ,the senario is very simple : the publisher send a JSON payload format that includes the encryption ...
1
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1answer
26 views

libsodium stream encryption [closed]

I am new to cryptography, I have used OpenSSL and its aes-256-cfb cipher before to do stream encryption, which works great. Now I am going to try ...
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1answer
31 views

C# equivalent of openssl ecparam -name prime256v1 -genkey -noout -out [closed]

I am having some issues generating a proper private key,I need it to be an Elliptic Curve private key suitable for use with NIST P-256 which i than need to convert to Base64-encoded private key in ...
2
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2answers
113 views

AES and ECDH key

I am trying to understand public key encryption. I found the table below in a paper online. I am struggling to understand the meaning of this. From the bits and pieces read, I am tempted to think that ...
2
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1answer
77 views

Why does DES use a block size of 64 bit?

Why do we use 64 bit as block size for the DES algorithm? Is there a reason not to use another block size, for instance 72 bits?
3
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1answer
44 views

How are the PC-1 & PC-2 calculated for the DES block cipher?

How are the permuted choice tables - PC-1 and PC-2 - calculated for the DES block cipher algorithm?
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1answer
37 views

What is a 'known answer test' (KAT)?

Came across this concept on while reading up on the key-encapsulation protocol SIKE but haven't been able to find a good explanation of what a known answer test is formally. What is a known answer ...
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1answer
29 views

Using AWS KMS to manage secret keys

For my use case, I need to maintain a secret key with the client to generate and verify HMAC for requests. We can have multiple clients and we can not make assumptions such as a client's server will ...
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0answers
36 views

dongle development [migrated]

I am to provide a hardware+software solution. The software is an application in c++ running on windows. The hardware is motherboard+processor+disk+memory. In order to protect the solution, I need to ...
2
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2answers
72 views

Does AES use different keys for each block of plaintext?

If you have 4 16-byte blocks of plaintext to encrypt does each block have a different 128 bit original key? Or do they all use the same?
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1answer
50 views

Encryption method that is purposely vulnerable to cracking parts at a time?

Is there a method of encryption where your key is made up of $n \cdot s$ bits, but also such that an attacker would know when they've successfully cracked each $s$-bit part? For example, the full key ...
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3answers
97 views

Encryption for IOT devices with minimal overhead

I have several IOT devices that transmits nearly 200 bytes of data every 10 seconds. I want to make the data secured but i also want to keep the data size nearly same. Ofcourse for IOT devices ...
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0answers
21 views

What are the advantages and drawbacks of using long term private keys compared to session keys?

What are the advantages and drawbacks of using long term private keys compared to session keys?
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1answer
57 views

How can a fully encrypted homomorphic program resist copying?

Let's say that we have an original homomorphically encrypted program with any possible code inside. What methods can it use to ensure that it is impossible to create an exact copy of it? Are there ...
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2answers
35 views

Multi Key Encryption but read only part of data

Is there a way to encrypt data/document with multiple keys, but every key is only allowed to read/decrypt only a certain part of the document and not the whole document? The document cannot be sub ...
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1answer
97 views

Is Bouncycastle RSA+OAEP implementation vulnerable to Manger’s attack?

I have written a code to encrypt a plaintext as below. Here I am using bouncycastle crypto provider and referring to the RSA+OAEP for that. ...
2
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3answers
185 views

Why is it impossible to find the private key from the public key?

From what I understand, based on the article A Beginner’s Guide: Private and Public Key Cryptography Deciphered, the public key is generated by performing $n$ tangent plus mirroring operations from ...
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3answers
64 views

Calculate the Number of active s boxes

I really want to learn how to calculate the number of active s _boxes for block cipher cryptographic algorithms. I want to do that manually after running each round of an algorithm such as LED ...
2
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1answer
43 views

Can I implement key recovery without compromising security?

I'm no crypto expert but I'm trying to figure out if this is possible: I'm building an application that has access to very sensitive user data. I receive this data in plain text but I'm not allowed ...
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0answers
30 views

Why is an error thrown in Python cryptography RSA decryption of encrypted AES key? [migrated]

I am trying to decrypt an AES key from a DER-encoded file that has been encrypted in RSA format. With the following code: ...
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2answers
105 views

How do I check if the output of my CFB TEA encryption algorithm is correct?

I have an assignment question regarding the TEA cipher in CFB mode. After much difficulty and research, I managed to produce an 8-bit TEA / CFB encryption algorithm. My input is supposed to be a ...
2
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2answers
84 views

What do people mean when they talk about forward secrecy in ciphers?

I've heard several people and websites talk about ciphers that have forward secrecy. I know about forward secrecy in key agreement protocols, e.g. RLWE, (EC/SI)DH, QKD, etc. This could be what they're ...
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0answers
80 views

AES 128 decryption with ciphertext shorter than key [migrated]

We are developing an application that has to work with data that is enycrpted by LoraWan (https://www.lora-alliance.org) We have already found the documentation of how they encrypt their data, and ...
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0answers
34 views

Decrypt SSL traffic with the OpenSSL command line [migrated]

I'm trying to do some manual data extraction/encryption/decryption with openssl command line. I've been reviewing RFC5246 to work out what I need to do. It is not crystal clear to me if I am going to ...
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2answers
43 views

Is an AEAD the recommended method to add encryption + HMAC to a protocol?

Assuming you are dealing with a competent developer/team, and you are advising on adding security to their protocol. Also for the time being lets not worry about the key establishment and validating ...
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0answers
38 views

Where shoul I store private/public keys and how should I share it?

I'm new in terms of encryption and I have to encrypt the data between two Java Spring applications, one have serves as MVC framework and other as Web Service, I'm implementing an asymmetric encryption ...
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0answers
61 views

What is the fastest way to generate truly random one time pad without electrical or any other complicated device?

I want to generate truly random one time pad as fast as possible but without the use of any electrical or any other complicated device. What is the fastest way to do that?