SHA256 给出 44 长度输出而不是 64 长度 [英] SHA256 giving 44 length output instead 64 length

问题描述

我正在使用以下代码来执行 SHA256.

I am using the following code to perform SHA256.

public static string GenerateSaltedHash(string plainTextString, string saltString)        
        {            
            byte[] salt = Encoding.UTF8.GetBytes(saltString);
            byte[] plainText = Encoding.UTF8.GetBytes(plainTextString);
            HashAlgorithm algorithm = new SHA256Managed();

            byte[] plainTextWithSaltBytes =
              new byte[plainText.Length + salt.Length];

            for (int i = 0; i < plainText.Length; i++)
            {
                plainTextWithSaltBytes[i] = plainText[i];
            }
            for (int i = 0; i < salt.Length; i++)
            {
                plainTextWithSaltBytes[plainText.Length + i] = salt[i];
            }
            byte[] bytes = algorithm.ComputeHash(plainTextWithSaltBytes);
            return Convert.ToBase64String(algorithm.ComputeHash(plainTextWithSaltBytes));                              
        }

当我使用 SHA256 时，我希望结果的长度为 64.但我得到了 44.

As I am using SHA256, I expect the length of the result to be 64. But I am getting 44.

这是什么问题?较短的长度输出会影响安全吗?

What is the issue? Will the shorter length output impact security?

推荐答案

Base-64 是每个字符 6 位 (2^6 = 64).

Base-64 is 6 bits per character (2^6 = 64).

256 bits / 6 bits per char = 42.6666 char

显然由于填充而最终变成了 44(您会在输出的末尾看到 1 或 2 个 =).

And that has obviously ended up as 44 due to padding (you will see one or 2 = on the end of the output).

您必须期待 base-16(也称为十六进制)，即每个字符 4 位(2^4 = 16).

You must be expecting base-16 (AKA hexadecimal) which is 4 bits per character (2^4 = 16).

256 bits / 4 bits per char = 64 char

对于十六进制使用这个:

return BitConverter.ToString(bytes).Replace("-", string.Empty);

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