'Hcrypthash ': Undeclared Identifier-similar error Solution

Compile a CPP Program When <wincrypt. h> is included, an error is returned. D: \ crypt. cpp (20): Error c2065: 'hcrypthash ': Undeclared identifier D: \ crypt. cpp (20): Error c2146: syntax error: Missing '; 'before identifier 'hhash' D: \ crypt. cpp (20): Error c2065: 'hhash': Undeclared identifier D: \ crypt. cpp (22): Error c2065: 'hcryptkey': Undeclared identifier D: \ crypt. cpp (22): Error c2146: syntax error: Missing '; 'before identifier 'hkey' D: \ crypt. cpp (22): Error c2065: 'hkey': Undeclared identifier D: \ crypt. cpp (24): Error c2065: 'hcryptprov': Undeclared identifier D: \ crypt. cpp (24): Error c2146: syntax error: Missing '; 'before identifier' hprov' D: \ crypt. cpp (24): Error c2065: 'hprov': Undeclared identifier D: \ crypt. cpp (32): Error c2065: 'cryptacquirecontext': Undeclared identifier D: \ crypt. cpp (38): Error c2065: 'cryptcreatehash': Undeclared identifier D: \ crypt. cpp (54): Error c2065: 'crypthashdata': Undeclared identifier D: \ crypt. cpp (70): Error c2065: 'cryptderivekey': Undeclared identifier D: \ crypt. cpp (105): Error c2065: 'cryptencrypt': Undeclared identifier D: \ crypt. cpp (151): Error c2065: 'cryptdestroyhash': Undeclared identifier D: \ crypt. cpp (157): Error c2065: 'cryptdestroykey': Undeclared identifier The reason is: The _ win32_winnt macro is not defined by default in vc6. In wincrypt. H # If (_ win32_winnt> = 0x0400) ... # Endif Solution: Add in stdafx. h # Ifndef _ win32_winnt # DEFINE _ win32_winnt 0x0400 # Endif