Cryptography is the practice and study of logical means used to achieve information confidentiality, integrity and authenticity. It covers, among other things, encryption (making some data unreadable except for those who know a given secret element, called a key), data hashing (in particular for ...

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Double encryption with home brew algorithm

Everyone says that home brew encryption is not a good idea because one day the algorithm will be known to attacker which sounds reasonable. So that seems it's main problem, on the other hand known ...
1
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1answer
57 views

Are encryption algorithms designed to hinder parallelization?

Are things like large memory requirements and constantly mutable state typically added to encryption alogrithms to hinder the ability of attackers to try multiple candidate keys simultaneously? Also, ...
1
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1answer
73 views

Basic XOR cipher for longer messages

How much effective strength is the following adding to a basic 512 bit XOR cipher? Private Key = Key0 consists of 512 randomly generated bits. This key is never used to encrypt or decrypt anything. ...
8
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4answers
555 views

What Country, State and City should I choose when requesting an SSL certificate?

I am really confused about the country, state and city I should select when submitting an SSL certificate. Should I provide the location of my servers or my current home address?I can always reissue a ...
2
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1answer
131 views

if a public key cannot decrypt the cipher text, then how can a private key?

I understand the "public" part of public key cryptography. Not the "private" part. For example, let's say our public key is %7 (modulo 7). And the message to be encrypted is 22. And we know that 22 ...
12
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5answers
2k views

Guessing random bit with 100% accuracy [closed]

I am soon to start my compulsory military service. I applied to the Cyber Warfare Unit of Finnish army. There was a test for applicants. Since the test is done the questions have now been published ...
1
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1answer
29 views

Is there a cryptosystem that allows a set of auditors to confirm that they have valid Shamir or Group signatures?

Suppose I have a client that generates and sends a Shamir key (or group signature) to a set of Auditors. This key is essentially an unverified set of bytes. Each auditor wants to somehow verify that ...
33
votes
2answers
2k views

How to start writing crypto software [closed]

This is just an academic question, I do not intend to write my own crypto software. Every time someone asks the question “How do I write my own Crypto?” the answer is don't. I'm currently studying ...
2
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1answer
53 views

What is the output length of CBC with zero input?

Given this formula for CBC encryption from 6.2 The Cipher Block Chaining Mode what is the output length of CBC if plaintext P is of length 0?
9
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2answers
187 views

What real life scenarios require separate end user certificates for Signing and Identity?

Based on this question, I'm interested in any rational argument that would support the idea of maintaining separate signing and authentication certificates. Conventional logic & wisdom says there ...
0
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1answer
59 views

Is RC2-CBC at all secure?

(And more generally, is there a site listing which various algorithms are still considered secure, so I wouldn't have to ask that here? Wikipedia's "known best attack" is not particularly clear.) I ...
8
votes
4answers
1k views

Is this RSA/AES combination good?

The team of developers I am part of is trying to develop a safe way to exchange sensitive data between a server and mobile devices. We have come up with the following algorithm: Device generates ...
2
votes
1answer
51 views

Is a Fernet token's timestamp a security risk?

A Fernet token has the following format: Version ‖ Timestamp ‖ IV ‖ Ciphertext ‖ HMAC As the above shows, the timestamp is not part of the ciphertext, so anyone can read the time the token was ...
3
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2answers
76 views

Is it possible to construct a specific AES collision?

Suppose I have a plaintext message P, and I encrypt it using key K to get ciphertext C. It's trivial to find a different plaintext message P' and a key K' so that the encryption results in C: just ...
4
votes
1answer
171 views

Can't get rid of “Your connection to website is encrypted with obsolete cryptography”

In my Nginx config I have: ssl_protocols TLSv1 TLSv1.1 TLSv1.2; ssl_ciphers ...
-3
votes
1answer
46 views

For which time-frame should we assume quantum computers? [closed]

It is generally known that we choose our key-lengths, so they are unbreakable in a specific time frame. For example we choose 112 bit keys (=2048-bit RSA) to protect data for the next few years and we ...
35
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2answers
4k views

How can it be easy to write but “impossible” to extract the private key from a crypto token?

A number of crypto-dongles make the claim that it is impossible to extract the stored private key once written. Yubico: The YubiKey AES Key information can never be extracted from a YubiKey ...
2
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2answers
67 views

Secure communication in SHTF

I am a prepper. I am preparing for a situation where there will be no rule of law and where I can't rely on the government for all my needs. This naturally involves storing food, water, and items for ...
3
votes
2answers
60 views

Requirements Placed on a User of a FIPS 140-2 Validated System

Per customer requirements, I am working with a FIPS 140-2 validated network switch that is actually running in FIPS mode. This guarantees that any cryptographic operations the device performs will be ...
1
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1answer
117 views

Understanding Key Serial Numbers (KSN) in Derived Unique Key Per Transaction (DUKPT)

I have a number of questions regarding Key Serial Numbers (KSNs) in DUKPT: KSNs are 8 - 10 bytes long. Older implementation are 8 bytes whereas newer ones are 10 bytes. Do I risk being incompatible ...
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0answers
18 views

Blinding to mask private key operations

Blinding is often used to mask private key operations when the underlying problem is integer factorization. For example, its used in both RSA and Rabin-Williams signature schemes. This presumes ...
2
votes
2answers
387 views

Why is there a “des-ede3-cbc” in my rsa private key?

I have created an OpenSSL RSA private key and certificate request with 4096 bit with the following command: openssl req -newkey 4096 When I view the private key with openssl asn1parse -in privkey ...
4
votes
2answers
259 views

How do cryptographic algorithms help hackers to bypass Antivirus software?

I was wondering how do hackers use cryptography for bypassing antivirus software. I don't have some deep understanding on how antivirus software works, but I know that every antivirus has base of ...
0
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2answers
174 views

Encryption Laws in India

Is cryptography legal in India? If yes, then what type of encryption is not allowed?
1
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1answer
68 views

Does WebCrypto also mandate the crypto algorithms be implemented in Javascript?

I am trying to understand what WebCrypto means. From what I understand it is - A Javascript Crypto API spec that all browsers must (hopefully) support. Am I correct? If so are the crypto algorithms ...
0
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1answer
40 views

Getting multiple key matches on plaintext/ciphertext pairs in double DES

I'm trying to implement a Meet-in-the-Middle attack and just to test it out I've done some hardcoding of values, which is simply this block of simple code: byte[] key1 = new byte[] { 0x20, 0x00, ...
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1answer
68 views

CryptoAPI to CommonCrypto with RC4

I have cryptographic code used in the Windows platform, which uses the Crypto API functions and need to convert this to using Common Crypto on OS X. Essentially the original code is this, with error ...
0
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0answers
45 views

Is there an encryption scheme that allows an auditor to view some, not all data?

I want to create an online chat room allows for privacy, freedom of speech, and for law enforcement to protect citizens from violent behavior. I think the best approach is to use Shamir secret ...
7
votes
1answer
196 views

Using RSA-SHA as/instead HMAC in OpenVPN?

While reading the manual of OpenVPN 2.3, I came across the --auth alg option. The manual says: Authenticate packets with HMAC using message digest algorithm alg. (The default is SHA1 ). HMAC is a ...
2
votes
1answer
78 views

Can TPM Storage Keys be Created Outside TPM?

I am interested in 'adding' preexisting keys to a TPM's storage hierarchy. An example of a desired key hierarchy can be shown as: (SRK)----->(User Storage Key)-------> User Working Key 1 ...
0
votes
0answers
98 views

Would it take long to brute force a md5 hash like this?

1be8917510-36.51929856278002 10bce1af27-99.18403192423284 103fa11cc6-87.21158325206488 Few examples above and as you can see the pattern is: 1xxxxxxxxx-{a percentage (0-100) to 14 decimal places} ...
1
vote
0answers
21 views

Checklist for Data Communication Review in ERP Solution

I am looking out for a checklist for data communication review within ERP application. I understand some of the checks would be related to digital signature, TLS/SSL use, Key Life Cycle management ...
66
votes
5answers
7k views

Why can't I MitM a Diffie-Hellman key exchange?

After reading the selected answer of "Diffie-Hellman Key Exchange" in plain English 5 times I can't, for the life of me, understand how it protects me from a MitM attack. Given the ...
1
vote
1answer
79 views

How to encrypt or store data so that only a pool of processes can share it on Windows?

I am writing an application T1 which is using SQLite database to store some sensitive data and i am trying to encrypt it securely. The issue i am facing is that i don't want my symmetric key to be ...
0
votes
1answer
22 views

Size of initialisation vector and plaintext in CBC mode

If I have a 16-number sequence (7,7,7,....7), and I need to encrypt this using a simple 4-bit substitution cipher, do I have to "chop" the plaintext in blocks which are of same size as the IV? In my ...
7
votes
4answers
352 views

Which strategy to encrypt data accessed by multiple users?

I need suggestions to design my database architecture (in the context of a web application) on the particular point of its encryption ; knowing that the following elements must be respected: 1- Data ...
7
votes
3answers
1k views

Why do we have such big keys?

In Chapter 7 of Applied Cryptography, Bruce Schneier claims that, due to thermodynamic limitations, "brute-force attacks against 256-bit [symmetric] keys will be infeasible until computers are built ...
5
votes
4answers
942 views

Client side encryption - only web browser available

I am creating an enterprise application, the server side runs a whole set of different apps, On the client side, there is only a webpage, no applet or anything else. Unfortunately data created by the ...
2
votes
2answers
248 views

Understanding salted password hashing using Java

Context: I am using this tutorial and trying to understand and implement salted password hashing using Java. After spending some time on this topic, I figured out that the basic idea is to: Convert ...
0
votes
2answers
52 views

Is there a way to give out secure tickets wihout storing them?

I'm building a website on which I want to make it very easy for users to create pages anonymously and later be able to come back and edit those pages. One way to do so is to give out confidential ...
0
votes
1answer
57 views

How to authenticate users?

I'm in the scenario that I'm planning a detailed description on "how to securely encrypt files" without putting too much in one Q/A. So, in a file-encryption scenario, what are the possible ways to ...
1
vote
1answer
20 views

Is the method of hardening the creation of a Cryptographically Generated Address (CGA) called hash extension

CGAs are sha1 hashes truncated to a 59 bit value. Along with a 3 bit security parameter they form a IPv6 address (more precisely the interface identifier). from wikipedia: The Sec parameter ...
4
votes
1answer
94 views

One time password question

Suppose F(X) = (5X) mod 9 is used to generate a one time password. I am supposed to generate the first 8 values using the above formula, starting with the seed value of F(5) Well I know that F(5) = ...
2
votes
3answers
226 views

How can two parties compare whether a simple (5 letter) shared word matches, without disclosing their word to each other?

I'm having some trouble with this scenario, some advice would be great. The context is that a group of people have each been give a simple 5 letter word - for example: Alice: ACTOR Bob: JEANS Dan: ...
4
votes
2answers
251 views

Sharing RSA keys between PGP and SSH protocols: Does this pose a security risk?

If I generate a PGP subkey that only has the authentication capablity and use this to generate an SSH keypair to authenticate Git for example, does this pose a security threat? When I do, should I ...
1
vote
1answer
61 views

Can DUKPT BDK be 192 bits?

All examples seem to be with 128 bits. Can it be 192 bits?
0
votes
2answers
89 views

Is there a cryptographic function that generates a reconizable visual pattern?

I have to build a system that will ultimately print a pass allowing access to a building. The validation of this ticket will be done manually (it can also be automatic but that's not likely at this ...
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2answers
97 views

How is encryption broken [duplicate]

The title describes pretty well what I want to ask, because I just can't wrap my head around it. I understand the basics of breaking encrypted data with the method of kind-of-bruteforcing where you ...
5
votes
1answer
181 views

How secure is CertiVox M-PIN?

CertiVox have designed a system with the aim of "getting rid of passwords". Essentially the system authenticates users with two factors of authentication: A 4 digit PIN and a token stored within the ...
0
votes
1answer
205 views

Google Chrome obsolete cryptography

I have a apache server running and following configuration for ssl: Header always set Strict-Transport-Security "max-age=31536000; includeSubDomains" SSLProtocol -all +TLSv1.2 SSLCompression Off ...