Questions tagged [encryption]

Encryption is the process of transforming plaintext using a cipher to make it unreadable to anyone except those possessing the key.

Filter by
Sorted by
Tagged with
175 votes
9 answers
614k views

How to determine what type of encoding/encryption has been used?

Is there a way to find what type of encryption/encoding is being used? For example, I am testing a web application which stores the password in the database in an encrypted format (WeJcFMQ/8+8QJ/w0hHh+...
user avatar
  • 2,234
68 votes
21 answers
66k views

Lessons learned and misconceptions regarding encryption and cryptology

Cryptology is such a broad subject that even experienced coders will almost always make mistakes the first few times around. However encryption is such an important topic, often we can't afford to ...
user avatar
163 votes
4 answers
136k views

Where to store a server side encryption key?

I have some data that is symmetrically encrypted with a single key in my database. Rather than hard coding it into my code, I am looking for a safer way to store the encryption key. Where can I safely ...
user avatar
  • 1,733
412 votes
14 answers
65k views

How is it possible that people observing an HTTPS connection being established wouldn't know how to decrypt it?

I've often heard it said that if you're logging in to a website - a bank, GMail, whatever - via HTTPS, that the information you transmit is safe from snooping by 3rd parties. I've always been a little ...
user avatar
76 votes
3 answers
11k views

Are URLs viewed during HTTPS transactions to one or more websites from a single IP distinguishable?

For example, say the following are HTTPS URLs to two websites by one IP over 5 mins: "A.com/1", "A.com/2", "A.com/3", "B.com/1", "B.com/2". Would monitoring of packets reveal: nothing, reveal only ...
user avatar
  • 5,042
114 votes
6 answers
45k views

Why should one not use the same asymmetric key for encryption as they do for signing?

In an answer to a question about RSA and PGP, PulpSpy noted this: It is possible to generate an RSA key pair using GPG (for both encryption and signing -- you should not use the same key for both). ...
user avatar
  • 27k
254 votes
12 answers
132k views

Why are hash functions one way? If I know the algorithm, why can't I calculate the input from it?

Why can't a password hash be reverse engineered? I've looked into this ages ago and have read lots on it, but I can't find the explanation of why it can't be done. An example will make it easier to ...
user avatar
  • 2,657
53 votes
2 answers
74k views

Decrypting TLS in Wireshark when using DHE_RSA ciphersuites

How can I decrypt TLS messages when an ephemeral Diffie-Hellman ciphersuite is used? I am able to expose the premaster secret and master secret from the SSL Client. Using that, how to decrypt the ...
user avatar
  • 771
22 votes
4 answers
1k views

Solution to the ‘Browser Crypto Chicken-and-Egg Problem’?

From time to time, questions come up in this board concerning web applications that utilize client-side cryptography (or ‘in-browser’ cryptography), where these applications claim to be designed in ...
user avatar
  • 19.3k
52 votes
2 answers
9k views

Digital Certificate deployment: using two certs for each user?

At a large enterprise environment I have come across a deployment approach for Digital Certificates where each user is issued two (2) key pairs: One for signing documents, emails, etc. that is ...
user avatar
  • 2,813
106 votes
5 answers
66k views

Is sending password to user email secure?

How secure is sending passwords through email to a user, since email isn't secured by HTTPS. What is the best way to secure it? Should i use encryption?
user avatar
  • 1,413
101 votes
5 answers
32k views

How can my employer be a man-in-the-middle when I connect to Gmail? [duplicate]

I'm trying to understand SSL/TLS. What follows are a description of a scenario and a few assumptions which I hope you can confirm or refute. Question How can my employer be a man-in-the-middle when ...
user avatar
  • 1,134
21 votes
3 answers
20k views

Is multiple encryption a good idea?

I know that many encryption algorithms, while secure, have vulnerabilities. To reduce risks, would multiple encryption like this Blowfish_CbC ( Rc2_OFB ( AES128_CBC (myfilecontent))) be a good idea? ...
user avatar
47 votes
5 answers
64k views

openssl: recover key and IV by passphrase

A large amount of files were encrypted by openssl enc -aes-256-cbc -pass pass:MYPASSWORD Openssl should derive key+IV from passphrase. I'd like to know key+IV equivalent of that MYPASSWORD. Is ...
user avatar
141 votes
14 answers
47k views

Is there any technical security reason not to buy the cheapest SSL certificate you can find?

While shopping for a basic SSL cert for my blog, I found that many of the more well-known Certificate Authorities have an entry-level certificate (with less stringent validation of the purchaser's ...
user avatar
29 votes
6 answers
6k views

Principle of asymmetric algorithm in plain english

I was giving a presentation to my colleagues about cryptography basics in which I explained about asymmetric algorithm and its use. One of the common question from the audience about asymmetric ...
user avatar
32 votes
5 answers
73k views

Compute the AES-encryption key given the plaintext and its ciphertext?

I'm tasked with creating database tables in Oracle which contain encrypted strings (i.e., the columns are RAW). The strings are encrypted by the application (using AES, 128-bit key) and stored in ...
user avatar
9 votes
3 answers
9k views

How to login and encrypt data with the same password/key

I've made a "vault" web app in PHP for storing passwords, credit card numbers, etc. It's mostly just for myself, but I'm practicing building it with multiple users in mind. I use two way encryption to ...
user avatar
71 votes
3 answers
121k views

How to estimate the time needed to crack RSA encryption?

How to estimate the time needed to crack RSA encryption? I mean the time needed to crack Rsa encryption with key length of 1024, 2048, 3072, 4096, 5120, 6144, 5120, 7168, 8192, 9216, 10240, 11264, ...
user avatar
  • 961
108 votes
5 answers
25k views

What kinds of encryption are _not_ breakable via Quantum Computers?

There's the recent article NSA seeks to build quantum computer that could crack most types of encryption. Now I'm not surprised by the NSA trying anything1, but what slightly baffles me is the word "...
user avatar
72 votes
3 answers
28k views

symmetric encryption session keys in SSL/TLS

This question concerns the session send and receive keys used in SSL/TLS protocol. my understanding is that this key uses symmetric encryption (DES, AES, BlowFish, etc.) I'm wondering, if public-...
user avatar
  • 1,190
38 votes
1 answer
10k views

Why can't I use the same key for encryption and MAC?

I wrote a simple file encryption program as an example of how to do encryption correctly, but after reading a questions about encryption + MAC, I think I made a mistake by using the same key for both. ...
user avatar
  • 2,858
47 votes
3 answers
11k views

Is there any advantage to splitting a password?

I've been reading about the LANMAN (LM) hash and I'm curious about a particular part of the algorithm. The LM hash is computed as follows: The user’s ASCII password is converted to uppercase. This ...
user avatar
14 votes
3 answers
4k views

Encrypt and Authenticate localhost-traffic?

I have some app-components on the same machine but in different languages which need to communicate. I am using socket communication over localhost to do so. The data transferred is confidential. ...
user avatar
497 votes
8 answers
493k views

RSA vs. DSA for SSH authentication keys

When generating SSH authentication keys on a Unix/Linux system with ssh-keygen, you're given the choice of creating a RSA or DSA key pair (using -t type). What is the difference between RSA and DSA ...
user avatar
  • 13k
238 votes
6 answers
286k 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 ...
user avatar
  • 2,703
179 votes
8 answers
40k views

Why can't the FBI read the key embedded in the iPhone's secure chip/ROM directly from hardware (silicon)?

As far as I understand, the 4 digit passcode is combined (in some fashion) with a key stored in secure read only memory (e.g. secure enclave chip or similar), where it is directly embedded into ...
user avatar
  • 1,689
68 votes
6 answers
28k views

Pattern to allow multiple persons to decrypt a document, without sharing the encryption key?

Current setup We have a service that allows users to upload documents through a website and stores the uploaded documents encrypted on disk. The documents on disk are encrypted with a per-user key, ...
user avatar
  • 1,092
28 votes
4 answers
25k views

Checklist on building an Offline Root & Intermediate Certificate Authority (CA)

Microsoft allows a CA to use Cryptography Next Generation (CNG) and advises of incompatibility issues for clients that do not support this suite. Here is an image of the default cryptography settings ...
user avatar
55 votes
5 answers
45k views

Are phone calls on a GSM network encrypted?

When I make a call on my cellphone (on a GSM network), is it encrypted?
user avatar
  • 1,988
23 votes
6 answers
17k views

Why do you need message authentication in addition to encryption?

I've been reading up on Authenticated Encryption with Associated Data. The linked RFC states: Authenticated encryption is a form of encryption that, in addition to providing confidentiality for the ...
user avatar
  • 345
6 votes
1 answer
8k views

In PSK TLS, how is the key used for encryption derived?

I'm trying to decrypt a message sent over a secure communication channel using TLS_PSK_WITH_3DES_EDE_CBC_SHA. I now have the client random number, server random number, PSK identity and PSK value. My ...
user avatar
23 votes
4 answers
13k views

Why does PGP use symmetric encryption and RSA?

Looking into the details of Pretty Good Privacy, I'm confused as to the reasoning behind encrypting the message with a session key and the key with the recipient's public key via RSA. I fail to see ...
user avatar
39 votes
3 answers
27k views

Block chaining modes to avoid

Everyone knows that ECB operation mode with a block cipher should be avoided because of clear and obvious weaknesses. But little attention is given to comparison of the other modes in the context of ...
user avatar
  • 81.9k
48 votes
4 answers
44k views

Can I use a private key as a public key and vice versa?

I have code to encrypt data using a public key and decrypt it using a private key. This is useful when a client wants to send data to a server and know that only the server can decrypt it. But say I ...
user avatar
58 votes
3 answers
49k views

When using AES and CBC, is it necessary to keep the IV secret?

If I encrypt some data with a randomly generated Key and Initialization Vector, then store all three pieces of information in the same table row; is it necessary to encrypt the IV as well as the Key? ...
user avatar
  • 683
31 votes
6 answers
38k views

What ciphers should I use in my web server after I configure my SSL certificate?

There are many great questions that ask what is the best certificate to use for a website; but once the certificate is purchased, there is also the possibility to choose or edit the Cipher list. ...
user avatar
52 votes
8 answers
22k views

Can an open Wi-Fi hotspot be considered "secure" when using a VPN connection?

There are many open Wi-Fi hotspots scattered around from cafes to airports. I understand that a non-passworded Wi-Fi leaves traffic unencrypted and therefore available for hackers to read. I also ...
user avatar
  • 3,041
27 votes
3 answers
11k views

How does non-ephemeral Diffie-Hellman key exchange become compromised in SSL when the RSA private key is leaked?

From my understanding, one of the major reasons we recommend Diffie-Hellman Ephemeral (e.g. DHE or ECDHE) over non-ephemeral DH, for SSL / TLS, is that compromise of the RSA private key (i.e. private ...
user avatar
  • 131k
27 votes
4 answers
3k views

Can a nation-state adversary perform a MITM attack by compelling a CA to issue them with fake certs?

As I understand it, with any encryption system based on a trust chain / CAs (eg SSL, TLS, S/MIME), it would be possible for a nation-state adversary (such as the NSA) to compel the CA to issue them ...
user avatar
  • 484
18 votes
3 answers
8k views

Encrypting user data using password and forgot my password

I am planning to do a web application which stores a lot of personal stuff (info, photos...). And to give users a sense of protection, I want to encrypt the data before storing it to the database. So,...
user avatar
  • 453
7 votes
3 answers
5k views

Digital Signature and Verification?

AFAIK , When Alice wants to write a message to Bob -- she uses Bob's public key and encrypt the message - and then Bob - using his private key - use to decrypt it. So public key is used to decrypt ...
user avatar
158 votes
7 answers
251k views

Why most people use 256 bit encryption instead of 128 bit?

Isn't 128 bit security enough for most practical applications?
user avatar
  • 2,877
168 votes
6 answers
21k views

Apple's open letter - they can't or won't backdoor iOS?

Apple released an open letter to the public outlining their reasons for not complying with the FBI's demands to modify the iPhone's security mechanism. Here's a summary: The FBI has an iPhone in ...
user avatar
  • 9,122
62 votes
7 answers
77k views

Asymmetric vs Symmetric Encryption

I am currently taking a Principles of Information Security class. While talking about different encryption methods, a large number of my classmates seem to believe that Asymmetric Encryption is better ...
user avatar
  • 1,080
35 votes
4 answers
20k views

What steps do Gmail, Yahoo! Mail, and Hotmail take to prevent eavesdropping on email?

I would like to ask what happens when an email is sent from Gmail, Yahoo or Hotmail public web email services? I don't understand email protocols in details, but as far as I know email traffic is ...
user avatar
  • 878
42 votes
4 answers
84k views

How (in)secure is POP/IMAP/SMTP

I'm making a few assumptions about basic email security, and I want to confirm or clarify some of these points to make sure I understand the big picture. Please correct me where I'm mistaken: The ...
user avatar
  • 523
38 votes
5 answers
10k views

How secure are my passwords in the hands of Firefox using a Master Password?

I'm relying on Firefox to remember my passwords, using a Master Password of more than 25 characters. How secure is this set-up?
user avatar
29 votes
7 answers
4k views

How to secure a WiFi network?

What do I have to do to secure a WiFi network? Is there any best practices? I have been recommended to use WPA2 encryption on the router, is that enough? What can I do to improve the security even ...
user avatar
  • 5,033
20 votes
4 answers
6k views

In what ways does Full or Partial Homomorphic Encryption benefit the cloud?

Can someone explain, in plain English, the practical ways FHE and PHE can be leveraged in the cloud? Some interesting (and confusing) links include this Microsoft Research PDF and this wiki entry. ...
user avatar

1
2 3 4 5
19