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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Identity-Based Encryption - how secure is it?

I was always taught never to invent my own crypto algorithm, and never to trust someone who has a proprietary algorithm. I'm looking at Voltage SecureMail, which uses IBE (identity-based encryption) ...
8
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3answers
712 views

zero knowledge proof and its protocol

In Zero-Knowledge Proof where we take the analogy of Peggy (Prover) and Victor (Verifier): In this story, Peggy has uncovered the secret word used to open a magic door in a cave. The cave is ...
2
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2answers
496 views

GOST cipher test vectors

Does anyone know where to find test vectors for the GOST cipher? I have been looking around for quite some time, and have been unable to find anything. I know that the sboxes are dependent on the ...
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4answers
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Using password hash as session ID?

For a rich client web app, on the server I need to verify that each call comes from a legally logged in user. Obviously user ID is not enough, because that's easy to guess. I have an idea I am ...
18
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4answers
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What to transfer? Password or its hash?

Let's say in my database I store passwords hashed with salt with a fairly expensive hash (scrypt, 1000 rounds of SHA2, whatever). Upon login, what should I transfer over the network and why? Password ...
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4answers
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Using computer random number generators to produce keys, it is secure?

Does generating an encryption key using the random number generator on one's computer present a security risk? If so how might that risk be mitigated, specifically when generating RSA key pairs in ...
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5answers
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Use RSA keypair for PGP encryption and decryption

Is there a way that I can use a RSA keypair with PGP? What I mean is that I have 2048 length keypair and i want to use that to encrypt and decrypt data. But all I have found is that the PGP uses some ...
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3answers
408 views

Would this kind of encryption be good at anything?

I have put much thought into this very simple algorithm and I have no clue if it was thought before... But I think it should have. I also know nothing about other encryption algorithms so I can't tell ...
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2answers
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mysql AES_ENCRYPT key length

AES_ENCRYPT uses a 128 bit long key to encrypt the data, but how does mysql handle longer or shorter keys? I found out that pycrypto for instances recomend to transform the key by using md5 sha1 sha2, ...
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5answers
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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 ...
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6answers
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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 ...
8
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4answers
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moving from MD5 to SHA-512

This question is more of a security policy than a technical security question. Many years ago I developed an asp.net site, implemented Forms Authentication, and stored the user passwords as MD5 ...
7
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1answer
268 views

Collision attacks on OCB?

I've been looking into the OCB cipher mode and everything I hear sounds good. I was planning on implementing it. Everything except for this lone voice, that is: Collision attacks on OCB: We ...
4
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3answers
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Vigenere Cipher - help with decryption (by hand)

So this is a Vigenere cipher-text EORLL TQFDI HOEZF CHBQN IFGGQ MBVXM SIMGK NCCSV WSXYD VTLQS BVBMJ YRTXO JCNXH THWOD FTDCC RMHEH SNXVY FLSXT ICNXM GUMET HMTUR PENSU TZHMV LODGN MINKA DTLOG HEVNI ...
4
votes
3answers
231 views

Choosing an authenticated encryption cipher mode without associated data

In the application I'm writing there is need for a huge amount of private data transfer on the order of eighty gigabytes, but there is no public data. I'm looking especially to gain ...
6
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1answer
2k views

What is the purpose of AEAD?

I think I need to correct some misunderstandings I have about AEAD. What is associated data used for in authenticated encryption?
5
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2answers
230 views

OMAC: multiplication in a finite field - how can I compute the correct polynomial

From The EAX Mode of Operation: We explain the notation used in the definition of OMAC. The value of iL (line 40: i an integer in {2, 4} and L ∈ {0, 1}n) is the n-bit string that is obtained by ...
3
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1answer
129 views

What is the benefit to using a two-pass AE scheme rather than one-pass?

What benefit is gained using a two-pass AE or AEAD scheme rather than a one-pass? Two-pass is roughly half the speed.
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4answers
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Are salted SHA-256/512 hashes still safe if the hashes and their salts are exposed?

Scenario: a database of hashed and and salted passwords, including salts for each password, is stolen by a malicious user. Passwords are 6-10 chars long and chosen by non-technical users. Can this ...
4
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2answers
138 views

A method for securely sharing centrally-stored documents among a changing set of users?

I believe it's possible to meet these requirements only if a third party is involved in a manual process. For example: Each user is given the same public key The private key resides offline at a ...
8
votes
3answers
593 views

Which authentication at the end of the Secure Remote Password protocol?

For the the client and server to prove to each other that they have the same premaster shared key, the original author suggests this: M = H(A | B | K) --> <-- H(A | M | K) ...
6
votes
1answer
3k views

Is this how to implement CTR around a system that only implements CBC, CFB, CTS, ECB and OFB?

The encryption library in my programming language does not support CTR, though it supports CBC, CFB, CTS, ECB and OFB. I'm assuming it is theoretically possible to securely implement CTR around one ...
9
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1answer
371 views

Optimal variable sizes in the Secure Remote Password protocol

I am implementing the Secure Remote Password protocol: U = <username> --> <-- s = <salt from passwd file> a = random() A = g^a ...
12
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3answers
2k views

When using AES and CBC, can the IV be a hash of the plaintext?

[Originally on programmers.stackexchange.com with title: Can you encrypt with AES+CBC and search the encrypted data] Basically, I'm going to go with Advanced Encryption Standard with either ...
5
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2answers
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Tool or Process to check for AES-NI support on processor?

In another question, Thomas' answer mentioned the AES-NI instruction set, which piqued my curiosity. Is there a tool or process available out there to check whether the instruction set is available ...
8
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1answer
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How to choose a stream cipher

Are there high-speed ciphers designed for things like internet streams without sacrificing security? There are so many options that operate in stream mode. How would one choose a cipher?
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2answers
631 views

Implementing Secure Remote Password: Constructing the verifier

The SRP protocol as described in RFC 2945 generates the password verifier: x = SHA(<salt> | SHA(<username> | ":" | <raw password>))` v = g^x % N I have three questions: why use ...
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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 ...
3
votes
1answer
93 views

Differing scrambling parameter generation methods in Secure Remote Protocol

RFC 2945 (The SRP Authentication and Key Exchange System) states, The parameter u is a 32-bit unsigned integer which takes its value from the first 32 bits of the SHA1 hash of B, MSB first. ...
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votes
3answers
1k views

Using Secure Remote Password without sending the username in the clear

To initiate a key exchange using the SRP protocol the client sends the username so the server can look up the salt and password verifier. Is there a simple way to change this so that an evesdropper ...
5
votes
1answer
267 views

Using Secure Remote Password without embedding the modulus

The SRP protocol as described by the author assumes that the large safe prime modulus and generator are embedded into the client and server rather than being transmitted as part of the protocol. ...
8
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1answer
711 views

Is a 2047-bit prime weaker than a 2048-bit prime?

I have a safe prime generator I'd like to speed up. I can benefit from a significant performance gain if the high order bit in the returned prime can be either 1 or 0. The returned prime would be ...
13
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2answers
840 views

How many iterations of Rabin-Miller should be used to generate cryptographic safe primes?

I am generating a 2048-bit safe prime for a Diffie-Hellman-type key, p such that p and (p-1)/2 are both prime. How few iterations of Rabin-Miller can I use on both p and (p-1)/2 and still be ...
30
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2answers
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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, ...
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3answers
2k views

How to exchange RSA public keys safely between two parties?

How to exchange RSA public keys safely between two parties via internet?
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6answers
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Security of SHA256 and Bitcoins

The Bitcoin network use SHA256 as a core component to it's design. I'm no expert on cryptography, but it seems to me it usually is only a matter of time before security vulnerabilities are discovered ...
7
votes
2answers
846 views

Any advantage to securing WiFi with a PSK, other than to keep out unauthorized

As I understand WiFi with a PSK, such as WPA(2)-PSK or WEP, anyone on the same network can decrypt anyone elses packets because everybody has the same key. In which case, if you are not going to ...
6
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1answer
2k views

Using TPM for full disc encryption?

E.g.: Can I make a better full disc encryption with e.g.: LUKS using the TPM? How?
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2answers
4k views

Simple way to encrypt files on Linux and decrypt on Windows?

We are in need of an encryption process for backups of very valuable data. This data will be stored on a distributed filesystem, so even with permissions set right, its not out of reach that this data ...
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2answers
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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 ...
38
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8answers
4k views

Why is HTTPS not the default protocol?

Why is HTTP still commonly used, instead what I would believe much more secure HTTPS?
6
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3answers
2k views

Is the OpenPGP private key inherently password-protected?

I know I am required to enter a password every time I use my OpenPGP key. Is this done via software implementation or is it a property inherent to the protocol, and therefore the key? Essentially, ...
17
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2answers
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Does my PGP key really need to match the e-mail address for which I'll be using it?

In considering whether or not I want to join the big web o' trust and put my keys on a key server, I got to thinking about how it would affect my e-mail address' exposure. I generally try to keep my ...
3
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1answer
396 views

Help on interpretation of FIPS-140 paragraph

This is from the FIPS 140-2 standard: Cryptographic keys stored within a cryptographic module shall be stored either in plaintext form or encrypted form. Plaintext secret and private ...
2
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3answers
661 views

Are the encryptions “broken” with great computing power?

http://www.dwavesys.com/en/pressreleases.html#lm_2011 Lockheed Martin Corporation (NYSE: LMT) has entered into an agreement to purchase a quantum computing system from D-Wave Systems Inc. I'm ...
8
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3answers
630 views

Most widespread use of PGP after 20 years

Phil Zimmerman released PGP (Pretty Good Privacy) on June 5, 1991. As we examine the legacy of that far-sighted and brave act 20 years later, what are the most widespread and helpful uses of PGP ...
16
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2answers
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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 ...
18
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1answer
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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 ...
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2answers
324 views

General Question on FIPS requirements

I understand that FIPS addresses cryptographic operations. My question is, is it addressing exactly this? For example, can an application loading a keystore use a non-FIPS provider? Any input or ...
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3answers
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Security implications of storing the password hash along an encrypted AES key

I am using the PKCS#5 standard to generate a key using a random and unique salt and the user's password in input. Consider this key as the "encryption" key. The "encryption" key is used to encrypt a ...