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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Do secure phone lines exist?

I could be out of context here about security, but , I would like to know if phone lines or phone calls over VOIP could be made secure . I know that Skype and other VOIP service providers have to ...
24
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2answers
12k views

How does RSA encryption compare to PGP?

On this answer ck says RSA and PGP are different. What you are essentially asking is how do I run my petrol car on diesel? The answer is you can't. I would be interested in a more ...
24
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3answers
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What is a cryptographic oracle?

I came across the term "cryptographic oracle" and despite a bit of googling I was unable to come across a clear, concise definition. What is a cryptographic oracle and what does it do? Can anyone ...
24
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5answers
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Why is Bruce Schneier recommending symmetric crypto over public key crypto

I just read the article written by Bruce Schneier, the crypto guru. In the article, he says : Prefer symmetric cryptography over public-key cryptography. But, he doesn't shed any light as to why....
24
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1answer
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Consequences of tampered /etc/ssh/moduli

What are the consequences if an attacker is able to modify the /etc/ssh/moduli file?
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4answers
3k views

NSA Suite A Cryptography: Security through obscurity?

What is the opinion of scholars, cryptographers on NSA Suite A? Containing unpublished algorithms. Could it really be that much better than the published algorithms besides being obscure and not ...
23
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2answers
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Why haven't (most of) the Zodiac Killer's letters been decrypted? [closed]

The Zodiac Killer (who, in fact, is not Ted Cruz) was a serial killer in the late 60's and early 70's. The twist is, he would frequently taunt the local press with cryptic letters. Four of these ...
23
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4answers
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how long does it take to actually generate rainbow tables?

I've been reading up about rainbow tables as I think they're quite interesting cause they're actually a pretty simple concept. Anyway, I was wondering, has anyone been involved in actually generating ...
23
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2answers
3k views

What is the purpose of frequently rotating TLS certificates without changing underlying keys?

I read in the OWASP cheat sheet regarding certificate / public-key pinning that “Google rotates its certificates … about once a month … [but] the underlying public keys … ...
23
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2answers
4k views

Is HTTP compression safe?

The CRIME attack taught us that using compression can endanger confidentiality. In particular, it is dangerous to concatenate attacker-supplied data with sensitive secret data and then compress and ...
23
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3answers
47k views

Secure Configuration of Ciphers/MACs/Kex available in SSH

Following on the heels of the previously posted question here, Taxonomy of Ciphers/MACs/Kex available in SSH?, I need some help to obtain the following design goals: Disable any 96-bit HMAC ...
23
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3answers
2k views

How does Convergence (CA replacement) prevent its notaries from being MITM'd as well?

I have been looking into Convergence and how it works, but I cant figure out how it is effective against a MITM attack that happens near the target system. My understanding is that Convergence works ...
22
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9answers
5k views

What cryptographic algorithms are not considered secure? [closed]

What cryptographic algorithms are not considered secure, but yet are still widely used and available in standard libraries? If applicable, mention a secure alternative.
22
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5answers
6k views

What's the practical limit for rainbow-table based bruteforce?

Say we have a hash of a password. The password can be considered to be made of of totally random characters and has a fixed length of N. The hash is SHA1(password+salt), where the salt is of length M. ...
22
votes
6answers
3k views

Shouldn't GPG key fetching use a secure connection?

If I run this for example: gpg --keyserver hkp://keyserver.ubuntu.com --recv-keys 0xFBB75451 then does the importing occur in a secure way? I mean does it go over only secured connections? (HKP?) ...
22
votes
3answers
7k views

Cracking a linear congruential generator

I was recently listening to the security now podcast, and they mentioned in passing that the linear congrunential generator (LCG) is trivial to crack. I use the LCG in a first year stats computing ...
22
votes
4answers
5k views

How would you store a 4 digit pin code securely in the database?

I'm familiar with password hashing, using salts, bcrypt etc. But it doesn't seem like this would work to store a 4 digit pin code since the attacker could try all 10,000 combinations quite quickly. ...
22
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3answers
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What specific padding weakness does OAEP address in RSA?

It's been recommended to use OAEP when padding messages to be encrypted via RSA, to prevent known plain text attacks. Can someone elaborate this in better detail? I'd specifically like to know the ...
22
votes
2answers
7k views

Is “real salt” the same as “initialization vectors”?

In the question about real vs. fake salt, the answers describe how real salt 'perturbs the encryption algorithm.' I know roughly how initialization vectors work; is this the same concept, or something ...
22
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3answers
4k views

Convergence - an SSL replacement?

Today, Moxie Marlinspike, a security researcher famous for his research on Android and SSL and related protocols (author of sslstrip/sslsniff), released "Convergence" which says is "an agile ...
22
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3answers
2k views

What ways are there to verify a self-written protocol?

Before everyone goes yelling: "NEVER DO YOUR OWN CRYPTO", I haven't, technically (I'm still half way), but apart from that I am making a TLS-like protocol, but way lighter. I needed to secure ...
22
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1answer
3k views

Timing attacks on password hashes

Timing attacks can have a devastating impact in scenarios where the secret is involved, often in cases where byte-wise array comparison is used. Now there are those that advertise using constant ...
21
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4answers
4k views

What are the chances to generate the same ssh key?

I could generate ssh keys on the client like (without password): ssh-keygen -b 8192 -t rsa -f /home/THEUSER/.ssh/id_rsa -P '' -v and copy the generated id_rsa.pub to the server: ssh-copy-id -i /...
21
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5answers
4k views

Can ECC be used without infringing on patents?

Can ECC (Elliptic Curve Cryptography) be safely used without infringing on Certicom's patents? I would like to make use of ECC in an embedded system to establish a secure channel. But, I am concerned ...
21
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1answer
2k views

Has SHA-3 Arrived?

I know NIST called for contenders (in 2007) regarding the new hash algorithm to replace SHA-2. Has there been a selection, or finalists selected?
21
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4answers
2k views

IPsec (Internet Protocol Security) facts

Internet Protocol Security (IPsec) is a successor of the ISO standard Network Layer Security Protocol (NLSP). What are the advantages, disadvantages, other interesting facts regarding the protocol?
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2answers
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What are the differences between the versions of TLS?

Please correct me if I'm wrong, but my understanding is that SSLv3 and TLSv1 is just a rename of the earlier protocol... but TLSv1 adds the ability to have secured and unsecured traffic on the same ...
21
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5answers
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PCI Encryption Key Management

(Full disclosure: I'm already an active participant here and at StackOverflow, but for reasons that should hopefully be obvious, I'm choosing to ask this particular question anonymously). I currently ...
21
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2answers
1k 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 using ...
21
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3answers
5k views

Why do PGP master keys only have a single subkey, and tie certification with signing by default?

After learning more about PGP subkeys and how to split apart the roles of (S)igning, (E)ncryption, (A)uthentication and (C)ertification, I discovered that in most cases(?) a default master key has a ...
21
votes
2answers
5k views

Describe an example of indistinguishability obfuscation or functional encryption

As described in Perfecting the Art of Sensible Nonsense, a major breakthrough in cryptography research was published in the summer of 2013: Candidate Indistinguishability Obfuscation and Functional ...
20
votes
5answers
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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 ...
20
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2answers
3k views

Why was DES with 112 bit keys (IBM) reduced to 56?

On the French wikipedia page about DES it says that the original DES algorithm from IBM used 112 bit keys. Why did they reduce this to 56 bits? Edit: ok NSA convinced IBM but today it seems like a ...
20
votes
6answers
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What are the good use cases for disk encryption?

I've been researching disk/file system encryption, and on the surface it seems like a good idea for a lot of things. But as I dig further, the security it offers seems more mirage like than real. ...
20
votes
4answers
18k views

Whats the difference between MAC vs hash

What is the difference between the two algorithms? One difference that I know of, is that MAC is keyed and hash is not.
20
votes
1answer
25k views

What is the actual value of a certificate fingerprint?

In a x509 digital certificate there is a "certificate fingerprint" section. It contains md5, sha1 and sha256. How are these obtained, and during the SSL connection, how are these values checked for?
20
votes
4answers
9k views

OS with encrypted RAM?

Are there any applications, JIT frameworks or operating systems that focus on encrypted virtual memory, or perhaps virtual machines that do something similar? I know there are processors (albeit old, ...
20
votes
3answers
7k views

How long should a random nonce be?

NIST provides good guidelines on the length of keys and hashes for various algorithms. But I don't see anything specifically on the length of a random or pseudo-random nonce (number used once). If ...
20
votes
1answer
16k views

4096 bit RSA encryption keys vs 2048

Where do 4096 bit RSA keys for SSL certs currently stand in terms of things like CA support, browser support, etc? In the overall scheme of things is the increased security worth the risk of 4096 bit ...
20
votes
2answers
2k views

Homomorphic encryption used for e-voting?

I was reading wikipedia about homomorphic encryptions, and one part got me a bit confused: "The homomorphic property of various cryptosystems can be used to create secure voting systems, ..." ...
19
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2answers
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What are the differences between MD5, SHA and RSA?

MD5 tools output hexadecimal values. In the same manner, do SHA and RSA together produce a hexadecimal (or any other) output? What are the differences between the MD5, SHA and RSA algorithms?
19
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2answers
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Why is it always `HASH( salt + password )` that we recommend?

Browsing over this site, many forums, online articles, there's always one specific way we're suggesting to store a password hash: function (salt, pass) { return ( StrongHash(salt + pass) ) } But ...
19
votes
6answers
29k views

Why is WPA Enterprise more secure than WPA2?

In personal mode WPA2 is more secure than WPA. However, I have read that WPA Enterprise provides stronger security than WPA2 and I am unsure exactly how this is achieved.
19
votes
3answers
3k views

What is the difference between “key length” and “bit strength”?

On occasion, I hear the terms "key length" and "bit strength" used interchangeably. Are these the same things? Or are they different?
19
votes
3answers
5k views

Computationally simple, lightweight replacement for SSL/TLS

Target hardware is a rather low-powered MCU (ARM Cortex-M3 @72MHz, with just about 64KB SRAM and 256KB flash), so walking the thin line here. My board does have ethernet, and I will eventually get ...
19
votes
2answers
7k views

How big should salt be?

I will be using scrypt to store passwords in my application. As such, I'll be using SHA-256 and Salsa20 crypto primitives (with PBKDF2). Having that in mind, how big salt should I use? Should it be ...
19
votes
1answer
7k 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? ...
19
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5answers
710 views

What concrete parameters can I change to make my passphrase-protected private gpg key more secure

There are several questions which discuss the resistance of passphrase-protected private gpg keys against brute force attacks. It seems, this kind of discussion could go on forever. Rather than ...
19
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1answer
2k views

WPA significantly less secure than WPA2?

I understand at least theoretically WPA2 is more secure than WPA, but in practice does it make any difference which one you use? From what I know there are no known attacks for either except for ...
18
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6answers
3k 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 ...