HMAC.m

function hash = HMAC(key,message,method)

% key:      input secret key in char
% message:  input message in char
% method:   hash method, either:
%           'SHA-1', 'SHA-256', 'SHA-384', 'SHA-512'

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

if strcmp(method,'SHA-1') == 1
    Blocksize = 64;
elseif strcmp(method,'SHA-256') == 1
    Blocksize = 64;
elseif strcmp(method,'SHA-384') == 1
    Blocksize = 128;
elseif strcmp(method,'SHA-512') == 1
    Blocksize = 128;
end

% if key length > Blocksize calculate Hash and format as binary
if length(key) > Blocksize
    Opt.Method = method;
    Opt.Format = 'uint8';
    Opt.Input = 'bin';
    
    Hash_key = DataHash(uint8(key),Opt)
    
    for i = length(Hash_key):Blocksize
        Hash_key(1,i) = 0;
    end
    key_bin = uint82bin8(Hash_key);
end

% if key length < Blocksize right pad with zeros and format as binary
if (length(key) > 0) && (length(key) < Blocksize)
    key_bin = str2bin8(key);
    L = length(key);
    for j = L+1:Blocksize
        key_bin{1,j} = [0 0 0 0 0 0 0 0];
    end
end

% if key length = 0 right pad with zeros and format as binary
if length(key) ==0
    for j = 1:Blocksize
        key_bin{1,j} = [0 0 0 0 0 0 0 0];
    end
end

% if key length = Blocksize format key as binary numbers
if length(key) == Blocksize
    key_bin = str2bin8(key);
end
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% format inner and outer padding as binary cell arrays
i_pad = [0 0 1 1 0 1 1 0];
o_pad = [0 1 0 1 1 1 0 0];
for i = 1:Blocksize
    i_pad_bin{1,i} = i_pad;
    o_pad_bin{1,i} = o_pad;
end
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% calculate key xor ipad and key xor opad
i_pad_key_bin = bit8xor(key_bin,i_pad_bin);
o_pad_key_bin = bit8xor(key_bin,o_pad_bin);
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Change format to uint8
i_pad_key_hex = bin82hex(i_pad_key_bin);
i_pad_key_uint8 = hex2uint8(i_pad_key_hex);

o_pad_key_hex = bin82hex(o_pad_key_bin);
o_pad_key_uint8 = hex2uint8(o_pad_key_hex);
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% concatenate (i_pad_key || message)
concat_i_pad = [i_pad_key_uint8,uint8(message)];
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Calculate Hash of i_pad_key||message
Opt.Method = method;
Opt.Format = 'uint8';
Opt.Input = 'bin';

Hash_i_pad_uint8 = DataHash(concat_i_pad,Opt);
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% concatenate (o_pad || Hash_i_pad)
concat_o_pad = [o_pad_key_uint8,Hash_i_pad_uint8];
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%


%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Calculate final Hash in HEX
Opt.Method = method;
Opt.Format = 'HEX';
Opt.Input = 'bin';

hash = DataHash(concat_o_pad,Opt);
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
end

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% FORMAT HELP FUNCTIONS
function bin = str2bin8(str)

for i = 1:length(str)    
    temp = dec2bin(str2num(sprintf('%u',str(i))),8);
    for j = 1:8
        bin{1,i}(1,j) = str2num(temp(j));
    end
end

end

function hex = bin82hex(bin)

hex = cell(1,length(bin));

for i = 1:length(bin)    
    string_bin = num2str(bin{1,i}(1,1)) ;
    for j = 2:8
        temp = num2str(bin{1,i}(1,j));
        string_bin = strcat(string_bin,temp);
    end
    hex{1,i} = dec2hex(bin2dec(string_bin));
end

end

function v = bit8xor(a,b)

if length(a) == length(b)
    for i = 1:length(a)
        v{1,i} = xor(a{1,i},b{1,i});
    end
else
    ERROR = sprintf('%s','Input cells must be the same length')
end

end

function out = hex2uint8(hex)

for i = 1:length(hex)
    out(i) = hex2dec(hex{1,i});
end

out = uint8(out);

end

function bin = uint82bin8(in)
bin = cell(1,length(in));

for i = 1:length(in)
    temp = dec2bin(in(1,i),8);
    for j = 1:8
        bin{1,i}(1,j) = str2num(temp(j));
    end
end
end
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