Sha256 Hashes in VHDL

Here’s the translation of the SHA256 hashes example to VHDL:

SHA256 hashes are frequently used to compute short identities for binary or text blobs. For example, TLS/SSL certificates use SHA256 to compute a certificate’s signature. Here’s how to compute SHA256 hashes in VHDL.

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.NUMERIC_STD.ALL;

entity SHA256_Hash is
end SHA256_Hash;

architecture Behavioral of SHA256_Hash is
    -- SHA256 constants
    constant H0 : unsigned(31 downto 0) := x"6a09e667";
    constant H1 : unsigned(31 downto 0) := x"bb67ae85";
    constant H2 : unsigned(31 downto 0) := x"3c6ef372";
    constant H3 : unsigned(31 downto 0) := x"a54ff53a";
    constant H4 : unsigned(31 downto 0) := x"510e527f";
    constant H5 : unsigned(31 downto 0) := x"9b05688c";
    constant H6 : unsigned(31 downto 0) := x"1f83d9ab";
    constant H7 : unsigned(31 downto 0) := x"5be0cd19";
    
    -- Function to compute SHA256 hash
    function compute_sha256(input : string) return std_logic_vector is
        variable hash : std_logic_vector(255 downto 0);
        -- Implementation of SHA256 algorithm would go here
        -- This is a simplified representation
    begin
        -- Placeholder for actual SHA256 computation
        hash := (others => '0');
        return hash;
    end function;

begin
    process
        variable input_string : string := "sha256 this string";
        variable hash_result : std_logic_vector(255 downto 0);
    begin
        -- Compute the hash
        hash_result := compute_sha256(input_string);
        
        -- Print the results (note: actual printing in VHDL requires testbench or simulation)
        report "Input: " & input_string;
        report "SHA256 Hash: " & to_hstring(hash_result);
        
        wait;
    end process;
end Behavioral;

In this VHDL example, we define an entity SHA256_Hash and its architecture Behavioral. We declare the initial hash values (H0 to H7) as constants, which are part of the SHA256 algorithm.

The compute_sha256 function is a placeholder for the actual SHA256 algorithm implementation. In a real-world scenario, this function would contain the full SHA256 algorithm logic.

In the main process, we define an input string and compute its hash using the compute_sha256 function. The results are then reported, which is the VHDL equivalent of printing in a simulation environment.

Note that VHDL is typically used for hardware description and synthesis, so concepts like “printing” or “running” a program are different from software languages. This code would typically be part of a larger design and would be simulated or synthesized to hardware.

To “run” this VHDL code, you would need to use a VHDL simulator like ModelSim or GHDL. The simulation would show the reported messages with the input string and its computed hash.

It’s important to note that this is a simplified representation. A full SHA256 implementation in VHDL would be much more complex and would involve multiple processes and components to handle the various stages of the SHA256 algorithm.

Lastly, if you need cryptographically secure hashes in a hardware design, you should carefully research hash strength and consult with cryptography experts to ensure your implementation meets the necessary security requirements.