How long is the SHA256 hash?

I'm going to run SHA256 on a password + salt, but I don't know how long to make my VARCHAR when setting up the MySQL database. What is a good length?

3

5 Answers

A sha256 is 256 bits long -- as its name indicates.

Since sha256 returns a hexadecimal representation, 4 bits are enough to encode each character (instead of 8, like for ASCII), so 256 bits would represent 64 hex characters, therefore you need a varchar(64), or even a char(64), as the length is always the same, not varying at all.

And the demo :

$hash = hash('sha256', 'hello, world!');
var_dump($hash);

Will give you :

$ php temp.php
string(64) "68e656b251e67e8358bef8483ab0d51c6619f3e7a1a9f0e75838d41ff368f728"

i.e. a string with 64 characters.

10

Encoding options for SHA256's 256 bits:

1. Base64: 6 bits per char = CHAR(44) including padding character
2. Hex: 4 bits per char = CHAR(64)
3. Binary: 8 bits per byte = BINARY(32)

2

I prefer to use BINARY(32) since it's the optimized way!

You can place in that 32 hex digits from (00 to FF).

Therefore BINARY(32)!

2

Why would you make it VARCHAR? It doesn't vary. It's always 64 characters, which can be determined by running anything into one of the online SHA-256 calculators.

3

It will be fixed 64 chars, so use char(64)

1

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