New answers tagged

1

Mark Buffalo has already provided an good answer on things to consider. However, I'd like to expand on his answer with few solutions, ofcourse it's extremely broad question so by all means this isn't remotely close to an "best" solution. It's just things to consider. I'll be making many assumptions based on this question and they will be: The operating ...


4

MD5-based anti-virus just doesn't work MD5-based anti-malware works decently against static-infections that never change. If it changes even by a little bit, you're screwed. However, MD5 is also vulnerable to collisions, so you're going to have a fair share of false positives. I wouldn't rely on this method at all. SHA-256 would probably be better for ...


0

The answer is NO, and it seems that you're mixing up two different things : Checksums and Hashes are one-way Integrity checkers. The purpose of their usage in that matter is to make sure that the data was not corrupted, and nothing else Recovery codes are the ones you're using if you need to recover your data by code provided. The most shining example is a ...


0

Hashes are designed to be one way. Its easy to travel from left to right, but it is practically impossible to travel from right to left when talking about Hashing.


3

For a login function, you should aim to get the hashing process to take around a second. If you take this post as a guide, 1170ms requires around 8,192 iterations of bcrypt (cost of 13). This means that your iterations add around 13 bits of effective entropy. If you have only 31 bits of entropy in a secret, hashed value, then this bcrypt configuration ...


0

There isn't a magic line beyond which hashing is useless. Rather, as you reduce the entropy of the input, the output becomes easier to guess. In this mail provider's case, they can add entropy using the salt. The larger the salt, the more entropy it will add.


1

Can this scheme be extended to work with hashed passwords somehow? Not this scheme. Because of how it works it needs to have the password or some specific equivalent (see http://stackoverflow.com/questions/1000281/storing-password-in-tables-and-digest-authentication for details) to do some necessary computations. Of course with a naive approach you ...


3

Am I right to say that this won't work if the password is not stored in plain text on the server? I fail to see how the server could verify the hash if the password is already hashed (with salt and pepper) on the server. This scheme does require the password to be stored in clear-text. Very bad. Can this scheme be extended to work with hashed ...


1

If you're using a secure channel namely TLS, you don't need to do these sort of tricks. About your first question, yes you're right, this scheme requires the server to have access to password in clear text to be able to reproduce H(nonce+cnonce+password). About your second question, I can't think of a way that won't open you up for replay attacks.(but I'm ...


1

This is essentially identical to simply generating a password that isn't hashed, in security terms. Whether you use your first name for a password or the checksum of the current time doesn't matter; if the thing you send over the Internet is compared with a string directly stored in a list on the server side, then the password isn't usefully hashed. The ...


2

I guess it depends on what the server does, but it doesn't add much protection either way (or is even worse). (Also, does the average user know how to compute a hash on mobile? Sounds quite a hassle to me.) 1. Server stores hashed password This means client sends H = hash(password) to the server, server looks up clients hashed password H' in the DB and ...


1

Would this increase security? No. Any modern application already stores it's passwords hashed in the database. Whenever an authentication attempt is made, the user input is hashed and compared with whatever's in the database. Mostly this happens with a 1-way encryption (the hash cannot be decrypted back to it's raw value). When you would create a hash on a ...


0

Email addresses are very often built off of easy to construct, common patterns with public data - first initial plus last name @ company, first name dot last name @ company, etc. etc. etc. Further, many actual email addresses have been leaked, and several sets of attackers are going to have stolen or purchased large lists of email addresses to try as well. ...


4

PBKDF2-HMAC-SHA-256 number of iterations desired = 1024 length of the salt in bytes = 16 length of the derived key in bytes = 4096 Ok - PBKDF2-HMAC-SHA-256 is a solid choice, though if you're running on any modern 64-bit CPU, I would strongly recommend PBKDF2-HMAC-SHA-512 instead, because SHA-512 requires 64-bit operations that reduce ...


0

Output size of RSA encryption always equivalent to RSA key size. In your case of Sha1RSA 2048 signing, 160 bit sha1 digest is padded as per PKCS#1 padding scheme in order make input block equivalent to RSA key size and then encrypted with RSA private key which results in 2048 bit signature.


0

First, simply look for offline password attacks against whatever software you're using that generated those unreadable passwords - at this stage, you haven't given any evidence that they're hashed vs. encrypted vs. scrambled some other way. Second, if it's open source, look up the source. In general, see if oclHashcat or John the Ripper (JtR) has a module ...


2

You seem to be confusing authentication with authorisation. OAuth is chiefly about authorisation and has various flows to support different scenarios and use cases, one in particular which overlaps with your question supports user / resource owner password based authentication for authorising the requesting application access to some set of resources. As ...


2

The hash that you posted has 32 hexadecimal characters. Each hexadecimal character is 4 bits, so this is a 128 bit hash (32*4=128). Some of the more common hash functions that produce 128 bit hashes are MD5 and RIPEMD-128. See here for others. However, as some of the other commenters have pointed out, hashes are designed to be difficult (if not ...


0

If you have the plain text password, you can probably find out which hashing algorithm was used. However, even if you do know which hashing algorithm was used, you will not be able to reverse a hash back into the password. This is exactly the point of password hashing: it is a one way algorithm. Think of the hashing algorithm as a mathematical meat ...


1

Tokens and passwords are really very different things. But you haven't specified in your question what you are really asking. You mention OAuth in the subject line of your question but then don't mention it again in the body of the question. OAuth has different kinds of tokens in its spec, depending on what sub-spec you're talking about and what kind of ...


2

OpenPGP also hashes the package content's, but additionally cryptographically signs the hash. A simply hash sum only allows to detect transmission problems. It does not allow to detect attacks, at least not as long as the hash is not verified through some secure channel. Given the signer's key was validated and is trusted, OpenPGP provides such a secure ...


1

The hashing function is used only to check package integrity for transmission errors (which is done by verifying its checksum). It cannot provide any way to authenticate the maker of the package. PGP can be used to verify the signature of the package (or of any other piece of data) over the maker's public key, hence certifying its provenience.


4

In security, there is an idea called the "CIA triangle", which stands for three basic security qualities: Confidentiality, Integrity, and Availability. Encryption generally addresses confidentiality, while hashing generally addresses integrity. Encryption is used to ensure confidentiality of communications, whenever confidentiality is important. It ...


5

If I understand your approach and code correctly then you simply don't use the original passphrase for "encryption" but a key derived from passphrase and a static salt. This approach of not using the original passphrase but a derived key is also called key stretching using a key derivation function. The purpose is to make a "better" key by hiding a not so ...


0

The key feature of hashes are that they are irreversible, so using this method to "decrypt" data would leave you in the same position that your adversaries are, which is brute-forcing the message. You might argue that you have the upper-hand in that brute-force competition by "knowing" the password that was used in the hash as a "salt" of sorts, but if you ...


1

When you install ADCS, you get the option of generating a new key pair, or reusing an existing key pair. The sentence you quote seems to indicate the latter: You export the certificate and private key from an existing CA, as a PFX file. You import the PFX into a Windows Server 2012 machine. You install ADCS on that machine, directing it to reuse the ...


1

Doesn't make that the hash almost useless ? Hashes serve integrity purposes in addition to a security purposes. Posting the hashes is a way for people to ensure their download wasn't corrupted. This used to be more of a problem than it is today, but still... Changing the contents of a file on the server is not a visible change. Changing the hash ...


1

Depends if the download and the hash are on the same server - it's not uncommon for downloads to come from CDN providers or systems like S3, which provide static file hosting, whereas the rest of the page comes from a CMS on a webserver with dynamic content. In this case, or where a file can be downloaded from an alternative source, it provides a good ...


2

You are thinking about problem the wrong way. One reason to have the hashes close to the download is to you detect if your download has been corrupted. It's not uncommon to have a corrupt download, so having the hash will verify if you downloaded cleanly. The other reason is that is common to a site host the files on another host, like a Content ...


7

The Information Commissioner's Office is the relevant public body. You can report a concern online. However, there is no explicit requirement to hash passwords. The Data Protection Act includes eight data protection principles; number is 7: Appropriate technical and organisational measures shall be taken against unauthorised or unlawful processing of ...


4

According to this article, the chosen prefix collision algorithm has been used to produce two executable files with the same MD5 hash, but different behaviors. Unlike the old method, where the two files could only differ in a few carefully chosen bits, the chosen prefix method allows two completely arbitrary files to have the same MD5 hash, by appending ...


1

Proving the existence of two different length plaintexts that collide using MD5 only requires you know that the number of inputs (and number of different lengths of inputs) are far greater than the number of possible outputs. Given that MD5 can receive inputs of any length and can only output a hash of size 128 bits, that means that for all strings of bytes ...


0

It is effectively impossible, due to information theory. Effectively impossible, as in "heat death of the universe" becomes a legitimate limiting factor on your search. You have a 2,000,000 byte (2MB) slice missing. A hash like SHA-1 has 20 bytes of information in it. By information theory, we should expect that there are 1,999,980 bytes which are still ...


0

It´ll basically take too long to achieve a satisfying result, addressing both: generating the missing video-part (according to computable criteria) and sorting the best ones out of them (that needs human intelligence or extremely high developed AI). Even if you finally have a nice video matching all criteria, you´ll never know if the original movie had the ...


1

A comment but it's too long: As others have shown, this isn't possible. However, there is a related problem that certainly is reasonable: Ok, you can't reconstruct that 200mb video that was split into 100 2mb files of which you have 99. However, you can create another file that will be a hair over 2mb that will allow you to reconstruct any one missing ...


1

It is hard if the underlying file has high enough entropy. If you know something about the underlying data, then you may well be able to recover it. For example, if there is a hacker anywhere in the vicinity it won't be long at all before someone tells you what I md5 hashed to get: 73868cb1848a216984dca1b6b0ee37bc However video usually has lots of ...


6

Let's say you have a computer that has infinite amounts of processing power, and can reliably check every possible message against every possible hash in a short time. Here's the problem you now face: collisions. What's a collision? Many different files can match the exact same signature. Many different messages can match the exact same signature. Hashing ...


58

A simple answer, NO. It is like asking, if I know, that x%4 = 3, is it possible to find the value of x? No. Surely, there would be infinite values of x satisfying this equation, but you wouldn't simply know which one is correct. Similarly, many(or infinite) video clips could result in a given hash value(obviously, infinite video clips have to be mapped to ...


12

This is not possible no matter how fast your computer is, simply because you cannot recreate the correct information out of practically nothing. You are actually asking for restoring 2 MB from 32 byte (size of SHA-256) or at most 64 byte (SHA-256 for chunk and for total file). This would be an ratio of 1:65536 or 1:32768. Given that video is already ...


6

You could not reproduce the file in any reasonable amount of time. The reason is that the only way to 'reverse' a hash is via brute-force, and considering how large the original file was, it would take you that exact amount of bytes to brute force. Let's say you have a video file that is 100MB large, precisely. 1MB = 1,000,000 bytes 100MB = 100,000,000 ...


1

Check the mask_attack page of the hashcat wiki. For your case: oclHashCat64.bin -m 2500 -a 3 -1 ?l?u?d ?1?1?1?1?1?1?1?1 [YOUR HASH OR HASH FILE] "-m 2500" specifies the WPA/WPA2 hash type, per hashcat documentation "-a 3" is the brute force attack mode "-1 ?l?u?d" says to use the character set of lowercase, uppercase, and digits (the character set you ...


0

The only data we have to work with is: input data and length output data and length Conceptually the output data itself should provide no information since cryptographic hash algorithms are not meant to convey information in their output. The only bit of information that's useful here is the length of the output data which is 105 hex digits indicating ...


0

If you're using it for file or message integrity calculations you can use CRC32, or if you're inclined to use a cryptographic algorithm you could just take the bottom or top bytes of any hash algorithm output - it'll be consistently reproducible and mostly unique to the data you hashed, though you'll be looking at a higher rate of collisions.


6

That question is impossible to answer without understanding your requirement for the hash function. Since we're in security.se, though, I suppose that you're asking for a secure hash function. In that case, I'm afraid the answer is: it can't be done. You see, a hash function is just a mapper: it persistently maps data of arbitrary size to a fixed-length ...


4

While I can't think of any reason as to why someone would restrict a hash to 10 bytes, if you really want to, I guess you can. What you could do is something like this answer: What is the best 32bit hash function for short strings (tag names)? where you get the md5 of the string and then truncate it to 10 or however many bytes. Honestly, unless if you can ...


3

Common reasons I saw: Outdated/insecure learning material: A great deal of books/online sites teaching PHP still teach using unsalted MD5 for passwords instead of bcrypt etc. I remember of about 201x a google search for "php password" returned mostly only such tutorials. Outdated knowledge of the programmer: many programmer don't keep their security ...


5

Gaining read-only access is a much more likely scenario than write access - after all, read access to an old backup or test server somewhere is nearly as good as read access to the real server. (since people don't change their passwords often enough) Also though, one account nearly anywhere (unless you're a banking site) isn't that valuable. Hundreds of ...


2

While using a sufficiently long and random salt will prevent a precalculation attack (eg: rainbow tables), it will not protect against a simple dictionary attack on the password. Consider the scenario where an attacker gets a copy of the database. If the passwords are just salted SHA2, it may be worth their effort to go after some number of the passwords. ...


2

Anything what the browser can do without human intervention can be automated. This might be done from outside by looking at the code or one might simply control the normal browser with Selenium or similar tools. Since you will pay users for visiting the page the chances are high that somebody likes to earn easy money and will automate the visits.


0

After for little research, I can say this extension is not safe because I can simply extract the main key in clear text format by using any type of HEX editor. Hash function is NOT important any more. Linux: Offset: 0x00003158 Using xxd Windows: Unable to compile but believe the develop team using default password 0123456789abcdef0123456789abcdef ...



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