It typically works like this:
Say your password is "baseball". I could simply store it raw, but anyone who gets my database gets the password. So instead I do an SHA1 hash on it, and get this:
$ echo -n baseball | sha1sum
Theoretically it's impossible to reverse a SHA1 hash. But go do a google search on ...
Length of the password, and size of the rainbow table, are red herrings. Size does not matter. What matters is entropy.
Rainbow tables are not really relevant here, for two main reasons:
Building the table is expensive. A table "covers" a number of possible passwords; let's call it N. There are N distinct passwords that will be broken through the table. No ...
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 ...
Technically you can still use a rainbow table to attack salted hashes. But only technically. A salted hash defeats rainbow table attacks, not by adding crypto magic, but just by exponentially increasing the size of the rainbow table required to successfully find a collision.
And yes, you'll need to store the salt :)
The news is full of examples of leaked databases (this is just the most recent results).
The vast majority of cases involve unsecured databases/backups (across pretty much all technologies: S3, mongodb, cassandra, mysql, etc....). These are usually due to configuration errors, bad defaults, or carelessness.
What data is leaked:
These generally ...
Your basic premise is wrong: a rainbow table is not just a compressed list of every possible hash lookup, and you do still need to do some hashing on the fly. Instead, it's a way of exploiting the nature of hashes to avoid storing the lookups in the first place, and minimise the amount you need to re-compute.
Wikipedia has quite a detailed explanation and ...
First of all, MD5 is not an encryption algorithm. It is a hash function. Encryption generally implies decryption, which you cannot do with a hash function.
Who said MD5 is good or unbreakable? It is 'breakable'. The complexity of obtaining a collision for MD5 is around 2^64. This is the equivalent of an exhaustive key search of 64 bits, quite weak for ...
It is not added after the hash. It is added before the hash, so the hash is completely different for every salt.
hash abcd = defg
store 123defg (for user with 123 salt) and 456defg (for user with 456 salt)
hash 123abcd = ghij
hash 456abcd = klmn
No. The compression doesn't work like traditional RLE or LZMA style compression.
Rainbow tables are, essentially, a lookup table which allows you to find a string given its hash. They're designed to be incredibly efficient at finding a hash in the index across billions of entries, while minimising disk space.
Now, imagine you're building a table for lots ...
Changing shift rounds blindly has undefined effect on strength. E.g., you could have similar amount of collisions, you could have orders of magnitude more amounts of collisions, shift rounds defined initially have known probability of collisions, shift rounds changed randomly do not.
Listen to folks above, use salting, it's specifically used to serve your ...
For password hashes, you need to use something like PBKDF2/RFC2898/PKCS5v2, Bcrypt, or Scrypt, all of which allow you to select an amount of iterations ("work factor"), rather than just one. PBKDF2, for instance, uses HMAC keyed hashing with a well known hash algorithm (typically SHA-512, SHA-256, or SHA-1) internally for a number of iterations, preferably ...
In addition to what tylerl said, it's important to stress that in modern crypto, salts are not used to protect against rainbow tables. No-one really uses rainbow tables. The real danger is parallelisation:
If you have no salt, or only a static salt, and I steal your DB of a million hashes, I can throw all my cores at bruteforcing it, and each core will be ...
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 ...
It's more secure because when multiple people have same password they will have different hash.
Simple implementation using Python:
passwordA = '123456'
passwordB = '123456'
And now let's add salt:
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 ...
In WPA/WPA2, the SSID of the network is used as a salt to the encryption. A rainbow table therefore is only useful if the SSID used to generate it is the same as the SSID of the network you are attacking. Using a common SSID increases this chance.
First, if two users use the rather weak password "baseball", then cracking one password doesn't help at all cracking the second password because of salting. Without salting, you've cracked two passwords for the price of one.
Second, rainbow tables contain pre-calculated hashes. So a cracker could lookup the hash of "baseball" in a rainbow table with a ...
If the hacker already has the password hashes, can't he just use them to hack the system?
Unless you're talking about NTLM hashes on windows environments (under certain conditions), the attacker would need to crack them. Not all systems permit using encrypted hashes for authentication.
Performing cryptanalysis against a hashed password consists of ...
Purpose and relevance
Rainbow tables help crack difficult passwords, i.e. those that can not even be found in a large dictionary. Passwords were historically stored as plain hashes in databases, and that's what rainbow tables are effective against: create a single rainbow table (slow) and run any number of databases full of hashes against it (fast).
First things first: this is NOT encryption. This is hashing. If your book talks of "encrypted hash" then that book is confused, and thus confusing. Notably, hashed passwords are never "decrypted", since they are not encrypted in the first place.
A cryptographic hash function offers a fixed output size. In the case of passwords, one needs to do something ...
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.
The value of salt is not in its secrecy, it's in its differentiation and the added complexity. You've touched on this a bit.
First, two passwords hashed with different salts have different resulting hashes. Therefore, an attacker cannot look at a password table and discover users who share the same password.
Second, as you write, a rainbow table could be ...
A stronger password is almost always better then a weak password. In the event of a breach the details of the hashing and salting of passwords become very important.
If the server used plain text, strong password and weak passwords are all equally and thoroughly.
If the server uses for example the infamous Microsoft LanManager hash string passwords won't ...
We need to know more about the reason for your question.
If you're a sysadmin or an auditor, and you want to use leaked lists and and dictionaries to check the strength of people's passwords prior to acceptance, that is a sound idea. Projects like zxcvbn that provide a password blacklist, plus a length requirement, provide at least a cursory assurance of ...
Well, the first thing is... what is a Rainbow Table?
A Rainbow Table is a list of the hashed values for the most common X# of passwords. 'Password', 'Password123', 'baseball', 'batman1', etc, etc - hash them all with the hash algorithm the target systems uses.
Then, check whether any column in the compromised SQL table matches any entry in the Rainbow table....
Generating rainbow tables is never the best way to attack a single instance. Rainbow tables are precomputed tables: you do a lot of computations in advance, under the hope that you will be able to apply these computations to several attack instances.
Precomputed tables (rainbow or not rainbow, this does not change anything here) all follow the same pattern:
Both hash tables and rainbow tables store precomputed hash values. Rainbow tables are a computing power vs storage tradeoff compared to hash tables. They are used because hash tables can grow very large especially as the throughput of cracking hardware has improved. You can brute force more combinations but now you need to store more.
How much space are we ...
MD5 is not "encryption" - it's a one-way hashing algorithm.
MD5 is not "unbreakable" - meaning of unbreakable here is open to interpretation; I'll take it as having security issues. Infact, MD5 is excluded from FIPS as not secure enough.
"every single possible combination of characters" - this equals infinity. And not even NSA can likely handle computation ...
WPA-PSK iterates your SSID and Pre-shared key through a HMAC-SHA1 hash function into a "raw" 256 bit key called the Pairwise Master Key (PMK). The PMK (which you are trying to brute-force) is presumably held by both the client and the router. When they are authenticating, they derive a key known as the Pairwise Transient Key (PTK) using: The client and ...
Assuming 256bit (32 byte) hashes and assuming you want to cover all possible passwords with 80 different characters (26 lowercase, 26 uppercase, 10 numbers, 18 other characters), these are the required rainbow-table sizes. I calculated this using the formula (80 ^ length ) * (32 + length).
However, keep in mind that the table below is for all possible ...