Sep 28, 2018 Good news is, Java has inbuilt support for generating the MD5 hash. Also Read: Java API to get Domain Authority and other Moz URL Metrics. You can generate MD5 hash in Java by making use of the API’s in the java.security package. Below is the code snippet to generate the MD5 hash. Mar 20, 2013 In this part, we will see some example to generate the MD5 hash in Java. Following Java program generates MD5 hash or digest of a String, by converting into a byte array. Java Security package provides MessageDigest, which can generate the MD5 hash. MessageDigest's digest method accept a byte array and return a byte array of hash value. Dec 24, 2019 Java provides a number of data structures for dealing with this issue specifically – for example, several Map interface implementations are hash tables. When using a hash table, these collections calculate the hash value for a given key using the hashCode method and use this value internally.
- Learn Java Secure Hashing algorithms in-depth. A secure password hash is an encrypted sequence of characters obtained after applying certain algorithms and manipulations on user-provided password, which are generally very weak and easy to guess. There are many such hashing algorithms in Java which can prove really effective for password security.
- Generate SHA or MD5 file checksum hash in java. A checksum hash is an encrypted sequence of characters obtained after applying certain algorithms and manipulations on user provided content. In this post, we will learn to generate the checksum hash for files.
A checksum hash is an encrypted sequence of characters obtained after applying certain algorithms and manipulations on user provided content. In this post, we will learn to generate the checksum hash for files.
1. Why we may want to generate checksum hash for a file?
Any serious file providers provide a mechanism to have a checksum on their downloadable files. A checksum is a form of mechanism to ensure that the file we downloaded is properly downloaded. Checksum acts like a proof of validity of a file so if a file gets corrupted this checksum will change and thus letting us know that this is not the same file or file has been corrupted between transfer for any reason.
You can also create checksum of file to detect any possible change in file by third party e.g. license files. You provide licenses to clients which they may upload to your server. You can cross verify the checksum of file to verify that license file has not been modified after creation.
Read More : MD5, SHA, PBKDF2, BCrypt examples
2. How to generate checksum hash for a file
To create checksum for a file, you will need to read the content of file byte by byte in chunks; and then generate hash for it using below manner.
This function takes two arguments:
- The message digest algorithm’s implementation
- A file for which checksum needs to be generated
You can use above function as below to generate MD5 file checksum :
To generate SHA file checksum, use the function as below:
Drop me a comment if something needs more explanation.
Happy Learning !!
Ranch Hand
posted 10 years agoGuys,
I need to generate a unique hash key for all users that are registering on my application and send them a confirmation email link that will activate their account. I'm considering to use UUID for generating the unique id. I'm trying to generate it based on the users email address. I would like to know if that would be a correct approach??
I'm trying something like:
I would like to know if this is this solid, secure enough or do I have to do more and use a Crypto kind of an implementation to acheive this??
I need to generate a unique hash key for all users that are registering on my application and send them a confirmation email link that will activate their account. I'm considering to use UUID for generating the unique id. I'm trying to generate it based on the users email address. I would like to know if that would be a correct approach??
I'm trying something like:
I would like to know if this is this solid, secure enough or do I have to do more and use a Crypto kind of an implementation to acheive this??
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Did a rm -R / to find out that I lost my entire Linux installation!
Did a rm -R / to find out that I lost my entire Linux installation!
Ranch Hand
posted 10 years agoI would like to know which one is better??
MD5
SHA1
UUID
MD5
SHA1
UUID
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Did a rm -R / to find out that I lost my entire Linux installation!
Did a rm -R / to find out that I lost my entire Linux installation!
Java Cowboy
posted 10 years agoThere is a contradiction in the term 'unique hash key'. Hash codes are not unique - a hashing algorithm will always have multiple possible inputs that result in the same hash code. (It's very easy to see theoretically why this is so - the hash code has fewer bits than the original data, so if there is a mapping from original data to hash keys, there must be some overlap). It's not possible to create unique IDs with a hashing algorithm. MD5 and SHA1 are hashing algorithms, so they do not guarantee that you get a unique output for any input.
UUID is a universally unique identifier. It is not a hashing algorithm.
Jothi Shankar Kumar wrote:
This will not work and will most likely give you an IllegalArgumentException. You cannot put any arbitrary string into this method - it has to be a string that represents an UUID (as returned by UUID.toString()). It's not a method that generates a unique ID based on arbitrary input.
If you're looking for something that creates a unique ID based on arbitrary input - such a method can't exist in principle. (If you invent a method that does this, then you have discovered the ultimate compression algorithm and you'll win a Nobel prize in information theory... See Jan Sloot).
Ranch Hand
posted 10 years agoSo how could I acheive a unique key for my case here?
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Java Cowboy
posted 10 years agoGenerate a unique ID, then store in a database somewhere which ID is associated with which user. When the user tries to activate the account using the ID, look the user's information up in the database.
You can create random unique IDs using the UUID class:
But, as I explained above, you cannot create unique identifiers based on some arbitrary input such as the user's e-mail address.
You can create random unique IDs using the UUID class:
But, as I explained above, you cannot create unique identifiers based on some arbitrary input such as the user's e-mail address.
author
posted 10 years agoJothi Shankar Kumar wrote:So how could I acheive a unique key for my case here?
Hash and unique key are two different things, but to answer your question...
If you want to generate a key for a single application, then the UUID class should be fine. If it is a group of applications, meaning that you can be generating it from many applications and on many machines -- then you probably need to create your own class that uses the host, pid, and probably system time. Regardless, it is probably best to use a service (such as a database) to generate the id.
Henry
Books: Java Threads, 3rd Edition, Jini in a Nutshell, and Java Gems (contributor)
Ranch Hand
posted 10 years agoJesper Young wrote:Generate a unique ID, then store in a database somewhere which ID is associated with which user. When the user tries to activate the account using the ID, look the user's information up in the database.
You can create random unique IDs using the UUID class:
But, as I explained above, you cannot create unique identifiers based on some arbitrary input such as the user's e-mail address.
You can create random unique IDs using the UUID class:
But, as I explained above, you cannot create unique identifiers based on some arbitrary input such as the user's e-mail address.
I understand what you meant here. But how unique is the randomUUID() generator?
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Did a rm -R / to find out that I lost my entire Linux installation!
Did a rm -R / to find out that I lost my entire Linux installation!
Java Cowboy
posted 10 years agoThe API documentation of class java.util.UUID explains that this method generates a type 4 (or version 4) UUID. The exact details of the algorithm are explained in RFC 4122.
For practical purposes, you don't need to worry that the generated IDs could be non-unique.
For practical purposes, you don't need to worry that the generated IDs could be non-unique.
Ranch Hand
posted 10 years agoSomewhat convincing answer here... http://en.wikipedia.org/wiki/Universally_Unique_Identifier#Java
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Did a rm -R / to find out that I lost my entire Linux installation!
Did a rm -R / to find out that I lost my entire Linux installation!
Rancher
posted 10 years agoJothi:
I'm not sure what you mean by 'somewhat convincing'. I went to the page, and it's not an argument, but an explanation.
John.
I'm not sure what you mean by 'somewhat convincing'. I went to the page, and it's not an argument, but an explanation.
John.
Ranch Hand
posted 10 years agoIt was convincing to me that the unique key that I'd be generating will not be a duplicate!
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Did a rm -R / to find out that I lost my entire Linux installation!
Did a rm -R / to find out that I lost my entire Linux installation!
Ranch Hand
posted 10 years agoJothi Shankar Kumar wrote:I need to generate a unique hash key for all users that are registering on my application and send them a confirmation email link that will activate their account. I'm considering to use UUID for generating the unique id. I'm trying to generate it based on the users email address. I would like to know if that would be a correct approach??
No it's not. The best way is to keep a global counter (starting at 0). When a user registers he/she gets the counter number as id, and then you increment the counter by 1.
In this way you're 100% sure each user gets a unique id. There is not other way to ensure that really.
Also, from a principle standpoint, the id's will be random. They're random in the sense that no user can know what number they're going to get.
Sheriff
posted 10 years agoGenerate Sha256 Key
Ulrika Tingle wrote:
Jothi Shankar Kumar wrote:I need to generate a unique hash key for all users that are registering on my application and send them a confirmation email link that will activate their account. I'm considering to use UUID for generating the unique id. I'm trying to generate it based on the users email address. I would like to know if that would be a correct approach??
No it's not. The best way is to keep a global counter (starting at 0). When a user registers he/she gets the counter number as id, and then you increment the counter by 1.
In this way you're 100% sure each user gets a unique id. There is not other way to ensure that really.
But you have to synchronize the counter, or you will run into problems in a multi-threaded environment. AtomicLong can help out here to do the hard work, with its incrementAndGet() and getAndIncrement() methods, the synchronized versions of ++l and l++.
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Ranch Hand
posted 10 years agoGuys, this seems to be running totally off the topic. I'm looking for a solution to send the user an email which has a registration key and it is this registration key that I have to generate uniquely for each user.
Why will I create a counter starting at 0 and increment that for each user when I store the user details in the database. Ofcourse I have the primary key. Don't I?
Why will I create a counter starting at 0 and increment that for each user when I store the user details in the database. Ofcourse I have the primary key. Don't I?
SCJP 1.4, SCWCD 1.4 - Hints for you, Certified Scrum Master
Did a rm -R / to find out that I lost my entire Linux installation!
Did a rm -R / to find out that I lost my entire Linux installation!
Rancher
posted 10 years agoGenerate Hash Key
a suitably large random string would work then. store the string in the DB, compare when they return.
It doesn't need to be unique if they send their email address too.
It doesn't need to be unique if they send their email address too.