![]() ![]() In fact, the only “entity” which would know the input to the hash function would be the end user who generated the password in the first place. This is unlike encryption in which given the output and the encryption key, you can know the input.ĭue to this one-way property, storing a hashed value of a password is a good idea since if their hash is compromised (via a database leak), the attacker would not know the original password (which is the input to the hash function). If you only know the output, it’s impossible/difficult to know its input. As you can see, the outputs are verify different.Īll in all, hash functions are “one-way functions”. Input sensitivity: A small change in the input (even just one character), should have a large change in the output string. Predictability: The hash function should always return the same output given the same input.įixed Length Output: The output of the hash function always has the same length (number of chars), regardless of the input’s length. This is slightly different from (2) since in (2), you are given one input, and in this case, you can cook up any input. Second preimage resistance: If an input to a hash function is known, it should be hard to find another input that has the same hashed output.Ĭollision resistance: This says that it is hard to find any two inputs such that their hashed output is the same. For example, if I take a random SHA256 hash output ( string data type) like "401357cf18542b4117ca59800657b64cce2a36d8ad4c56b6102a1e0b03049e97", it should be very hard to know what the input to the hash function was that resulted in this output. Preimage resistance: Given the output of a hash function Out, it should be hard to find any input In, which when hashed, results in the same output ( hash(In) = Out). ![]() ![]() They are functions that have these properties: This is where hashing or hash functions come into play. Using these keys, the attacker would be able to decrypt the encrypted passwords - making this method of storage weak. However, if the database is compromised, then the encryption keys would probably be compromised as well. Using encryption may seem to be a good choice since the attacker would not know the actual passwords (because they are encrypted). This rules out storing passwords in plain text. The aim behind storing passwords securely is that even if the database containing them is compromised, the attacker can’t decipher any user’s actual password. To make matters worse, users tend to reuse passwords across services which makes storing them securely even more important. Feel free to share if you found this useful □.Storing passwords can be a nuance due to the liability of them being compromised. We have now successfully hashed our string using the md5 algorithm ✅. hash the string // and set the output format const hash = md5Hasher. We can define it using the digest() method on the object returned from the update() method like so, // get crypto module const crypto = require( "crypto") Finally, after calling the update() method we need to define the output format for the hash. It is called update() since it also accepts a continuous stream of data like a buffer. hash the string const hash = md5Hasher. It can be done like this, // get crypto module const crypto = require( "crypto") createHmac( "md5", secret) Īfter creating the hasher, you need to use the update() method in the hasher and pass the string to hash the string. create a md5 hasher const md5Hasher = crypto. In our case, it is md5 as the first argument and the secret as the second argument to the method. Now we need to call the createHmac() (The Hmac in the method stands for Keyed-Hashing for Message Authentication □) method to create the hasher and pass the hashing algorithm's name we need to use as the first argument and the secret or salt string as the second argument to the method. secret or salt to be hashed with const secret = "This is a secret □" string to be hashed const str = "I need to be hashed using MD5□!" get crypto module const crypto = require( "crypto") Now let's make a string that needs to be hashed using the md5 hashing algorithm and also make a secret or a salt string that needs to be provided with a hashing function to add more secrecy □. To create a MD5 hash, you need to import or require the crypto module and use the createHmac() method in Node.js.įirst, let's require the crypto module in Node.js, // get crypto module const crypto = require( "crypto") ![]()
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