1、参考https://qna.habr.com/q/232342

2、代码

uses
  hash, HMAC, HMACSHA2;
  
function GetSign: string;
var
  i: Integer;
  key: string;
  values: string;  
  HMacContent: THMAC_Context;
  mac: TSHA256Digest;
begin
  key := '2018';
  values := '2020-10-13&1234'
  
  hmac_SHA256_init(HMacContent, PChar(key), Length(key));
  hmac_SHA256_updateXL(HMacContent, PChar(values), Length(values));
  hmac_SHA256_final(HMacContent, mac);

  Result := '';
  for i := 0 to Length(mac) - 1 do
    Result := Result + Format('%.2x',[mac[i]]);
end;