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 ...

learn more… | top users | synonyms

1
vote
1answer
31 views

RSA public key and private key lengths

I have a lot of problem with understanding the size of RSA public key and its private pair. I saw different key sizes for RSA algorithm (512, 1024,... for example) but, is this the length of public ...
0
votes
1answer
59 views

What can I do if someone is using my IP address? [on hold]

Another device in my network is using my IP address, what can he do if he is using my IP address? Is this a crime? Can him be caught by police or sue by Malaysia government?
2
votes
2answers
182 views

Using OAuth 2.0 without token storage

I am building a system for a product which requires Authentication and Authorization. Naturally I have chosen using OAuth 2.0 as it is a commonly used protocol and has proven to be useful. I am ...
1
vote
0answers
30 views

Cryptographic enforcement schemes using Diffie-Hellman [migrated]

If one wants to set up a decentralized cryptographic enforcement scheme in which the level of 'confidentiality' of information is marked by its position in a poset, why not use Diffie-Hellman to ...
1
vote
1answer
45 views

SSH Key: Ed25519 vs RSA

A lot of people recommend using Ed25519 instead of RSA keys for SSH. The introduction page of Ed25519 (http://ed25519.cr.yp.to/) says: [..] breaking it has similar difficulty to breaking [..] RSA ...
28
votes
7answers
16k views

Where can I learn cryptography/cryptanalysis the hard way, without going to school ? Any good book?

I'm not so bad at mathematics: I know what are p-list and p-combinations, I know matrix algebra, I know what a XOR is, I know how to tell if number is a prime, etc: I'm not the programmer who hates ...
18
votes
2answers
39k views

Security comparsion of 3DES and AES

Which one is more secure and least possible to be broken through cryptanalysis AES or 3DES (no matter performance)? I need to use encryption for my projects to store and secure sensitive information ...
2
votes
2answers
98 views

Are hashes of hashes used for password storage in practice? Why/why not? [duplicate]

A naive developers might store a password in the database directly, which would then be compared directly with the password sent from a client. A more security conscious developer might instead store ...
2
votes
2answers
160 views

How to store derby database encryption key in HSM?

The Derby Database supports encryption with a key or password. Traditionally this key is stored in the file systems, now I am looking to store and protect this key in the HSM instead, but I couldn't ...
10
votes
5answers
13k views

What does “key with length of x bits” mean?

I'd like to know what it means to say "the cryptosystem C uses keys with a length of x bits". I do not understand what the bits length means... doesn't it depend on the encoding? The same word encodes ...
24
votes
12answers
3k views

Can a file contain its md5sum inside it?

Just wondering if it is possible to create a file which has its md5sum inside it along with other contents too.
14
votes
1answer
5k views

Where do I get prime numbers for Diffie-Hellman? Can I use them twice?

I realise it's very hard to generate suitable prime numbers and generators for the Diffie-Hellman key exchange. What is the best way to generate them? And if I have one, can I use it twice? ...
1
vote
1answer
59 views

Is HTML5 sessionStorage secure for temporarily storing a cryptographic key?

Assume I am building a local web application (e.g. browser extension) in HTML5 to encrypt a database locally. Access to the database is controlled by a password and a cryptographic master key is ...
13
votes
6answers
1k views

Does prepending a salt to the password instead of inserting it in the middle decrease security?

I read somewhere that adding a salt at the beginning of a password before hashing it is a bad idea. Instead, the article claimed it is much more secure to insert it somewhere in the middle of the ...
1
vote
2answers
51 views

Can I use AES CTR mode to encrypt files with same key and nonce?

I want to encrypt the files stored in SD card and I am using the CTR mode of AES to encrypt it. The key and IV are fixed. So each time I encrypt/decrypt I use the same key and nonce. Most of the ...
-2
votes
1answer
49 views

Crypto for penetration test [closed]

I'm a newbie but I want to become a penetration tester. I'm taking a course on cryptography but I'm wondering... how useful is crypto for penetration testing compared to other skills like operating ...
5
votes
3answers
126 views

Does TLS_FALLBACK_SCSV provide blanket protection against downgrade attacks?

The TLS_FALLBACK_SCSV flag was touted as a way to prevent POODLE, which abused the potential to downgrade to SSLv3 from TLS. Does the implementation of this flag prevent similar downgrade attacks ...
2
votes
1answer
28 views

How can the parallelization in CTR mode be attained?

I am using CTR mode to encrypt/decrypt files. Theoretically CTR mode is faster than CFB or CBC because of its individual operations on blocks. In my case CTR mode takes almost as long as CFB. How can ...
-2
votes
0answers
20 views

Topics to start an interest group at our company [closed]

Good afternoon everyone, I'm looking to start a Communities of Practice at my job. Our company is largely involved in application development for our customers but we also want to get into, what my ...
1
vote
0answers
39 views

What is the difference between XOR and poly-XOR? [closed]

What is the difference between XOR and poly-XOR in encryption?
5
votes
3answers
319 views

What steps can you take to make offline cracking of SRP harder?

In the aftermath of the Blizzard hack, what steps can I take to make offline cracking of SRP more difficult? My question assumes that your database is already gone and that you implemented SRP more ...
-1
votes
1answer
54 views

Cryptowall encryption files

This is a question concerning the way the Cryptowall ransomware encrypts files on the victim's computer. Someone knows if it is possible to recover the encryption key comparing the encrypted file and ...
1
vote
3answers
92 views

Sharing a common public and private SSH keys for a cluster of machines

I guess this is way to settle an internal debate I am having with myself. In my provisioning process, I am wanting to share a common public and private ssh keys for each machine in a clusters, ...
1
vote
1answer
51 views

Prevent padding oracle attack on key exchange process

I found in my searches that the padding oracle attack can be used against the RSA with PKCS1PAdding or OAEP padding, and I used this algorithm for a symmetric key exchange. How can I prevent a padding ...
3
votes
2answers
74 views

Can the intended recipient be derived from a public-key encrypted ciphertext?

Assuming you have a list of possible recipients' public keys, and a ciphertext encrypted with one of those public keys, would it be possible to determine which public key?
18
votes
5answers
934 views

How can I explain “zero knowledge proof” to an end user?

A ZKP allows proof of knowing the answer to a secret, without actually disclosing what that answer is. Is there any analogy that can help people put this concept into everyday practice? A "lie to ...
5
votes
1answer
85 views

How does combining SHA256 with RIPE-MD160 compare to SHA256 + SHA-3?

Bitcoin stores its addresses as a combined SHA256 + RIPE-MD160 hash. Is it correct to assume this is done to prevent a failure in the algorithm? Since SHA3 was designed to be an alternative to ...
1
vote
1answer
8k views

Encrypting string in JavaScript and decryption in Java [closed]

I would like to know if there is any library to do encryption in JavaScript and decryption in Java. I have already tried many APIs, but am not getting the same values in Java. I want public-private ...
0
votes
1answer
48 views

RSA: same symbols in plaintext give same symbols ciphertext?

I just started studying Information Security, but I just ran this program: http://www.sanfoundry.com/cpp-program-implement-rsa-algorithm/ and faced this strange thing. For small keys (don't try to ...
0
votes
2answers
209 views

Asymmetric vs Symmetric Encryption Benchmarks

I have found these benchmarks in Crypto++'s site. http://www.cryptopp.com/benchmarks.html But I am, quite honestly, not entirely sure how to interpret them. I am really looking for a set of ...
0
votes
0answers
39 views

Designing a security system for road pricing

It's my first semester with Information Security and I still feel a little lost. Sorry in advance for stupid mistakes I may have made. the examples in round brackets below are my own ideas, wrote ...
6
votes
1answer
511 views

can multiple encryption of data with multiple keys increase the security?

I mean: does encrypting data multiple times have an effect on diffusion and confusion? Does it increase security, or does it have no effect? Is it useless? Does it make it harder to break the secret, ...
50
votes
3answers
56k views

Is Telegram secure?

There is a new WhatsApp-killer application called Telegram. They said that it's open source and that it has a more secure encryption. But they store all the messages in their servers and WhatsApp ...
3
votes
2answers
177 views

Encrypting USB traffic: Is RSA necessary for AES session key exchange when using pre-installed secret keys?

I need a solution to encrypt USB communication between device A and device B. I was thinking about configuring each device with a secret RSA-2048 key, which would be used to exchange an AES-256 ...
3
votes
1answer
130 views

How does OTR's authentication using “Question and answer” protect against MiTM?

I've read that the answer has something to do Socialist Millionaire, but I still don't understand how can the user be protected against malicious Man In The Middle, which would capture the question ...
3
votes
1answer
126 views

Is this symetric or asymetric encryption?

I’m at the beginning of my journey into the world of security. I am reading about the most fundamentals topics and I have encountered something unusual that has thrown me. The Conundrum: I have come ...
2
votes
1answer
329 views

Requiring 2 keys to access a content

I need to use an external service that can only be accessed by password. I don't like the idea of storing the plaintext password on the server, but AFAIK there's not much I can do. Considering this ...
4
votes
3answers
43 views

GnuPG symmetric encryption yields different output

I have a use case where I want to commit symmetrically encrypted source code using GnuPG (think of Coursera assignments for backup and collaboration). I encrypt/decrypt all sources in a batch with a ...
63
votes
6answers
11k views

Why shouldn't we roll our own?

Why shouldn't we create our own security schemes? I see a lot of questions around here about custom crypto and custom security mechanisms, especially around password hashing. With that in mind, I'm ...
1
vote
3answers
36 views

What type of hashing method is used for the private key to encrypt for signing messages?

To use RSA for signing, Alice takes a hash of the message, encrypts the hash using her own private key, and appends the result (this is the signature) to the message. Eve can of course still ...
0
votes
1answer
123 views

Is it dangerous to use the same key (RSA) for both encryption (PGP) and authentication (SSH)?

Alice wants to send an encrypted message to Bob, but she also wants to connect to Carol's server. Are there any dangers associated with using the same RSA key for both PGP and SSH (other than a lack ...
-1
votes
0answers
32 views

InvalidKeyException using ECPublicKey [migrated]

I'm getting the following exception when i try to encrypt a byte array with a EC public key : java.security.InvalidKeyException: No installed provider supports this key: ...
16
votes
2answers
982 views

Is it okay to sign a PGP key without an IRL meeting?

[PGP] can get paralyzed by excessive analness. — Phil Zimmermann Preamble I am in the process of building my own web of trust. That is, I want people (PGP users…) to be—fairly—sure that, by ...
0
votes
0answers
124 views

Client authentication with a collection of open source distributed servers

With a collection of open source distributed servers, all sharing every users data. How can the user authenticate with any server, without the passwords being compromised by a malicious server? ...
0
votes
1answer
88 views

Analyzing a TLS connection?

Suppose I want a secure TLS communication between me and myschool.edu. Which of the following should I trust to preserve confidentiality, integrity, and authenticity. Here are the options and my ...
26
votes
6answers
25k views

Most secure password hash algorithm(s)?

What is/are currently the most cryptographically secure hashing algorithm(s)? (available in PHP) Speed is irrelevant, because I'm iterating the hash over a fixed time (rather than a fixed number of ...
0
votes
1answer
105 views

Prevent CryptoLocker on Server

A quick question, which may have a not-so-quick answer - Are there any ways to prevent files associated with CryptoLocker, to be propagated to a data server, by means of a back up? We use Cobian as ...
44
votes
6answers
6k views

How do some sites (e.g. online banks) only ask for specific characters from a password without storing it as plaintext?

I thought How can a system enforce a minimum number of changed characters... would answer my question, but it seems this is a different case. When I sign on to my online banking account, I'm prompted ...
4
votes
0answers
31 views

At what point can you you implement crypto algorithms? [migrated]

First off, this feels like it should be a common question, so I'm sorry if I've missed an older thread. Note that in my question, I'm talking about "implementing AES" rather than "designing AES2" or ...
0
votes
1answer
124 views

Can you recover the password from ZipCrypto encrypted ZIP file?

I know that "legacy ZIP-crypto" is not secure and you can get at the contents of the file quite easily. Now the question is, can you also get at the password (assume this is a very long, very high ...