When using SHA256 it always returned me characters contained in the standard english alphabet(lowercase) and arabic numbers(0-9). So the character set returned was [a-z]U[0-9]

The reason this confuses me is that I've heard a SHA256 should have 2^256 different results, since each bit is "random" each byte should be represented by a completely random ASCII character, not one that fits into a restricted set of 36 characters(26 letters and 10 numerals)

Basically, I want to know if my SHA256 is behaving properly and if it is, why is it like this. I am using the standard sha256sum function that comes with linux.

CodePudding user response：

Yes, your assumption is correct. SHA256 will generate a total of 32 bytes (= 256 bits), each byte having an arbitrary value between 0 and 255 (inclusive).

But here lies the problem, most of those bytes do not represent valid ASCII characters (only 0 - 127) and some of them are invisible (space, tab, linefeed, and several control characters).

To "render" the SHA256, the bytes are encoded in hexadecimal format. A single byte is represented by 2 characters. 00 = 0, 7f = 127, ff = 255.

The SHA256 hash of the empty string is e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855, or if each byte is converted to decimal:

227 176 196 66 152 252 28 20 154 251 244 200 153 111 185 36 39 174 65 228 100 155 147 76 164 149 153 27 120 82 184 85