A hash algorithm is a function which takes a variable size input and produces a fixed size output. The algorithm tries to make it difficult to predict the output for a given input, find two inputs with the same output, or reconstruct the input from the output.

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Am I right by changing the default algorithm on a web app?

Numerous clients have told me that my suggestion on changing the algorithm on a web app does not increase security. I've tried reasoning that if the files have not been exposed, the attacker has to ...
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2answers
786 views

What is the advantage of using a symmetric cipher like AES to generate a keystream?

I see examples of AES (with a shared secret key) being used to encrypt shared secrets (e.g. nonce + counter) to produce a keystream against which the plaintext is XOR'ed to produce the ciphertext. ...
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2answers
435 views

Should I decode a base64 password before hashing for storage?

My server gets base64 encoded passwords from the client, and I am going to hash them for storage in a credentials table. Should I decode the password and hash the clear text password, or just hash ...
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1answer
89 views

Using multiple hash-functions along the line [duplicate]

I was wondering what the effect on strength/security is If I would use an aggregate of multiple hash-functions. For instance, I don't want to sent passwords in plain text (although it's over an ...
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2answers
351 views

How can I store a password history to prevent reuse?

I have an application with a user database. The database stores the password using a bcrypt hash with a randomized salt. How can I implement a password history set (to prevent password reuse) in a ...
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96 views

What is this encrypted with or where can I find examples of encryptions to compare it with? [closed]

I have a hash thingy I am trying to decode and I have done relatively little with encryption, though I would like to try to learn some more. The hash is: 1YMTpavsFq7ykllC3CCsg3e1li31re1nROxuW1wqIqpk ...
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0answers
24 views

How is password character validation in 3D secure is implemented? [duplicate]

We have a website which stores hashed passwords in the database. During logins we hash the password entered by user and compare two hashes. This is quite standard so far. Our client which is in ...
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2answers
663 views

Is it safe to use PBKDF2 for hashing?

I would like to get a few opinions on whether it would be safe or not to use PBKDF2 to generate a hash of a password. For my purposes I'd like to assume that the hash itself will be posted on the ...
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1answer
721 views

Is every hash format that nginx accepts for HTTP Basic Auth weak against brute force?

According to http://nginx.org/en/docs/http/ngx_http_auth_basic_module.html nginx can read password hashes of these types: crypt(), apr1, SHA1 & SSHA. This is how I understand how these hashes ...
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2answers
154 views

Using public key infrastructure or hashing for personal identification privacy?

I've been reading about identity theft recently, and I'm wondering about some possible solutions using the techniques of asymmetric/symmetric/hashing in encryption. My idea is going to cross those 3 ...
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3answers
461 views

Why not hashing and salting passwords?

When I was implementing my webapp, I decided to hash and salt users' passwords in order to protect them, even though I knew that there will never be a lot of them ... if any. Of course, I'm not saying ...
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1answer
124 views

Is it a good idea to hash a string and use it as a passphrase?

Is it a good idea to hash(SHA-512/whirlpool) some simple memorable string and use it for passphrase(for LUKS/TrueCrypt container), instead of using just a string like t4k#La93Fs(5w5) as a passphrase?
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2answers
219 views

Rainbow Tables: What is the Reduction Used for?

This is a follow up from this answer. The answer is very good, and it put me to thinking and doing some research. I have found another good explanation on this site. At some point, the author says: ...
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1answer
139 views

Rainbowtable - Start with plain text [duplicate]

I know how to use rainbow tables. I've already read the other questions this topic here. Well but there is still one question left. As an attacker, I usually have a hash value of a password and ...
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1answer
159 views

using counter instead of salt for hashing

I'm developing own protocol for secure message exchanging. Each message contains the following fields: HMAC, time, salt, and message itself. HMAC is computed over all other fields using known secret ...
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0answers
65 views

Does the ordering of encryption and hashing matter? [duplicate]

I am now learning keyed hash function, where A and B share a secret key k. I want to know if the ordering of encryption E and hashing H matters? i.e. Is there any difference between H ◦ Ek (m) and Ek ...
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1answer
118 views

Password sending through network [duplicate]

In case of no TLS/SSL available, why can't I use the hash of the password (SHA512) as the key to encrypt the password (with out any salt) to send through the network ? MITM attacks I can understand, ...
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4answers
539 views

Irreversible hashing without collision

We are looking to allow users to log on with a smart card. The smart card reader can read the smart card ID and send it to us. We are, however, not allowed to store the smart card ID. Not in ...
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5answers
601 views

Use the hash of the password to encrypted password

I have a app which transmit the password in clear text. I was planning to use the hash of the password (SHA-512) as the key for encrypting the plain text password. Then send the encrypted text to the ...
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1answer
584 views

Does bcrypt on top of md5 reduce its security?

A GitHub project I recently checked has a flawed security as they're using an unsalted md5() to hash the passwords. I opened a bug and they acknowledged it. However, the transition from md5() to ...
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0answers
240 views

How do I convert from this weird John/Asleap format to lc (for HashCat)?

I'm trying to setup a system for pen-testing. I'm using the FreeRadius-WPE patch to collect Challenges/Requests from people who connect to my spoofed AP instead of the actual network. Here is the ...
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2answers
204 views

How secure are hashed passwords that are salted too?

SAP Netweaver has its passwords hashed and also salted. But I read that a tool such as John the Ripper can bruteforce them. So how does security varies when passwords are hashed, in particular in the ...
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4answers
400 views

usernames and passwords

I was thinking about usernames and passwords and I was wondering how secure it would be to instead of the server having a list of usernames and accompanying hash of the passwords, just have a list of ...
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1answer
276 views

What key to use in HMAC

I need to use HMAC on a certain message to guarantee integrity, but I cannot figure out what are the requirements for the key to be given as input to the hashing algorithm. In particular I have to ...
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6answers
843 views

Is it useful to protect hashed password with encryption?

Imagine that I am hashing the users' passwords with a random, long enough, salt, using key stretching, and a secure hash. Would it be more secure to finally encrypt the hash with a symmetric key?
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3answers
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symetric key encryption vs hashing

This is a fascinating document: top 100 passwords from adobe breach I have a question about one part of it: However, thanks to Adobe choosing symmetric key encryption over hashing, selecting ...
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1answer
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MITM vs. data leakage

We are designing a web API - accessible via https only - but two schools of thought seem to have arisen among our team: Group 1 wants to adopt an approach that is more concerned about data leakage ...
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4answers
453 views

How to tell if a site is securely storing passwords? [closed]

A site I frequent has a policy to make you change your password every 90 days. That's a cool policy, but I stumbled upon an old xkcd and facepalmed myself, because lots of doxing happens on this site. ...
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3answers
533 views

Is there a hash algorithm that can identify similar files or strings?

Is there a hash algorithm that will help you identify similar files or strings? For example, the hash for ABC and XBC would be similar rather than radically different as is usually the case. I know of ...
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1answer
581 views

Reversing a block hash of SHA-1 with known Plaintext?

Is it possible to reverse the hashing of a block in a Datastream fed to an SHA1 if the plaintext for that block is known? If it is not possible (which I assume) does it make attacks to retrieve the ...
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3answers
292 views

Brute Force In Order Or Random?

Which is faster, on average to find the original plain text of a hash: brute force in-order, or with random plaintexts?
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2answers
279 views

scrypt strength with “weak” salt

I'm working on a project where following constrains apply: There's no remote database or any other means of storing extra data like random salt When user logins in, only username and password are ...
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4answers
677 views

At what point does adding more iterations to PBKDF2 provide no extra security?

If my true passphrase is used only to generate a hash which is used as the cipher's actual key, doesn't that mean it's possible to try and brute force the cipher itself? I know it would take an ...
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1answer
1k views

Are there sha 512 rainbow tables available? [closed]

Are there sha 512 rainbow tables available for download or what kind of dimensions and processing power would be required to generate them?
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1answer
689 views

Reverse-engineering password salts

Lets set out a scenario, a database has been dumped and all the passwords are hashed. You notice that some users seemed to have signed up twice and have the same hash. You run these hashes through ...
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1answer
73 views

Payload authentication + HW-SW Binding

I want to authenticate a (2nd stage) bootloader during the boot process using a symmetric key, which is derived from HW properties of the platform the bootloader is running on. Thus, I want to bind ...
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1answer
505 views

Is this password hashing + salt method the most secure way possible? [duplicate]

I am just wondering what all the security experts think of my method for password hashing. I want to come up with a method I can use for all my future web development projects. First I create a ...
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3answers
390 views

comparing password hashing algorithms - PoC ideas?

OK so I just started working for a security consulting firm and we recommend SHA 256 (with salt) for password hashing because MD5 is too weak. I have read some brilliant answers (the list is too ...
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2answers
172 views

Would multiple exposed bcrypt hashes of the same UUID v4 with random generated salt be too insecure?

I'm looking into implementing an ownership check on JSON objects and want to avoid going back to the database to ensure ownership of said object/record (i.e., to prevent a user from updating an ...
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2answers
514 views

Does using Bcrypt to encrypt credit card numbers satisfy PCI compliance?

I understand that using MD5 is not safe and is not PCI compliant. Does using BCrypt satisfy PCI compliance
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4answers
547 views

How can I be secure with a global salt?

If I understood the basic of password hashing and storing, what we need are: a "strong" salt a "real" random salt a unique salt per password a password hashing function with a high CPU cost We ...
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1answer
2k views

Brute force password cracking with a GPU

How are GPU's provisioned for password cracking? Do all, if not most cracking programs have special GPU aware software or do they just function at the basic driver or API level of the device? Can it ...
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2answers
1k views

How can I check the integrity of the downloaded files?

I know we use hash functions to check for the integrity of the files etc... but my question is how can we check for the integrity of the files being downloaded from some server?
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1answer
313 views

The Hash header in GPG ASCII armor

When sending a signed message using GPG, it always includes a line that says Hash: SHA256 right at the top of my email. I was wondering if/why it's required, and if not, how I can remove it (in an ...
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2answers
553 views

Algorithm to generate NTLMv2 Hash in PHP

I am trying to develop a PHP function to calculate NTLMv2 hash by providing server & client challenge, domain, account and password. The resulting hash appears to be not correct. Can someone ...
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4answers
660 views

Secure authentication: partial client-side key stretching… please review/criticize my idea

I am trying to figure out what would be the 'perfect' authentication system for a website. On one end, we know that simple hashing algorithms can be brute-forced or cracked in other ways. Hence why ...
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2answers
274 views

Could a user never store a password if a username/email hash was used instead?

So I was just thinking about token_authenticatable setup from devise (rails gem), and this thought occurred to me: Could we strengthen web security by hashing username/password with javascript before ...
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1answer
287 views

Challenge, Authentication and session key

I programmed an application on Linux using C, I added an authentication and cryptography layer that's going like this : 1 -client sends connection request. -server send a random challenge to client. ...
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John the ripper passwd file format with salt not working

I'm trying test password strength in one of our e-commerce sites. I'm using john the ripper to brute-force a password file. The algorithm used by PHP is: $hash = md5($salt . $pass) No other ...
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2answers
333 views

Is there any way to cryptographically hash a human thumbprint?

Is there any way to cryptographically hash a human thumbprint into a form that can be consistently reproduced by thumbprint readers? Assuming that it would be possible to create a database of ...