What is the best SHA algorithm?

Is SHA-256 still secure?

I understand that for block ciphers, "security" is based on the assumption that they are one-time pad ciphers.

Can someone explain why SHA-256 can be attacked using the birthday paradox? I've been reading a lot of articles but none seem to be able to explain the reason in a way that I can understand. As you noted, there is a standard way to attack such ciphers, by generating a large enough number of ciphertexts and then looking for collisions, assuming the cipher is one-time pad. The birthday paradox has nothing to do with it, but is a separate attack vector. If we assume that the hash function (SHA256) is secure, then the only real concern would be to generate a large enough set of ciphertexts to see if the collision attack can be used to find a message that hashes to two different messages. Once you've done that, you can use other known attacks against any other block cipher (eg the padding oracle attack).

If you look at the birthday attack, we take a number of messages, k, and run through them until we find two that hash to the same message. The real question, of course, is whether SHA256 is secure. In order to answer that, we need to know exactly what it is that we're hashing. If it's a block cipher, then all that means is that it will be insecure if someone can find two keys that produce the same value when applied to a block. In that case, you could use a block cipher like AES-256 instead. In general, though, if someone can break SHA256 for some other reason, they can break SHA256 for any use, so using it for encryption is rather pointless.

Which is better, SHA-256 or SHA-512?

I found two implementations of the SHA256/SHA512 functions: one in the Bouncy Castle library and one in the Apache Commons utility library.

Which one is more suitable for cryptography? And why? Also, are there any other libraries available for such basic functions? For the cryptographic functions that are currently provided in the Java standard libraries (there is a list here): If you need only a single cryptographic operation for your code, then you can use the existing algorithms. That is, use the built-in hashing algorithms: SHA1, SHA-2 family, SHA-3 family (SHA-384, SHA-512), MIIX or the CRC32, or MD5.

In your case, it appears you need to run multiple operations, so you will have to use a library that provides better performance than the Standard Java Libraries. It also doesn't matter what algorithm you are using, they all provide the same results as far as the security properties are concerned.

It's worth knowing that many libraries offer both SHA-256 and SHA-512. Bouncy Castle has been offering a "SHA-512" since 2026, but not since 2026. If I remember correctly, some C# implementations provided sha-256 too, but most have moved to SHA-512 by now.

What is SHA-1 and SHA-256?

Introduction.

First of all, ? SHA-1 and SHA-256 are the 2 strongest hash functions on the market right now. They have been compared to each other several times (link) with both SHA-256 having a higher hash speed than SHA-1, but lower collision resistance. In this tutorial you will learn about their properties, their weaknesses, their advantages and disadvantages.

First of all, there are 5 different types of hashes: MD5 - 128 bits. SHA-1 - 160 bits. SHA-256 - 256 bits. SHA-512 - 512 bits. SHA-384 - 384 bits. Let's take a look at these hashes and their strengths and weaknesses now. MD5 was originally patented in 1994, but it was found that an algorithm for a 16 bits hash function existed as early as 1990. Although it was patented in 1994, by 1998 the patent had expired so the author of MD5 decided to make it available to everyone.

In short, MD5 is a secure digest of a message. It computes a 128 bit number which serves as a signature for this message. The idea is quite simple: just convert your text file into a message, MD5 it and get the MD5 hash out of it. This 128 bit number is called the message digest. We can do this with any other message as well, we can compute MD5, MD4, MD6 or any other hash out of any number of bytes. MD5 and MD4, however, are only capable of hashing a single file.

SHA-1 was derived from MD5 (more information on this can be found in the Derivation from MD5 chapter below). It basically copies the entire design of MD5.

As it follows, SHA-1 is a strong candidate for a hash. The problem is that it can run into problems if a computer becomes compromised, although it is unlikely to happen. One of these compromises can be a remote access Trojan that intercepts and records the communications with your server.