https://github.com/novacoin-project/novacoin/pull/6

Not accepted yet, but ready for testing. It introduces metahash field which contains a hash of transaction metadata.

alex@alex-VirtualBox:~/novacoin/src$ ./novacoind gettransaction 989aaba0866c361efa36ab465a6632db23cd4ef3337984e8947b39caa4136ab8
{
    "txid" : "989aaba0866c361efa36ab465a6632db23cd4ef3337984e8947b39caa4136ab8",
   "metahash" : "391141273c9fa47a7bf52b7980aa1208aafa9453d468b6d37186a57c537066bf",
   "version" : 1,
    "time" : 1392845428,
    "locktime" : 0,
    "vin" : [
        {
            "txid" : "c63e334bbe74b1d928dcb01543353cb04026d2ae556e6876655ef074b786036e",
            "vout" : 1,
            "scriptSig" : {
                "asm" : "304402203ed3b29bdfcc1a7e55e635b855605110c540c0d8f2d2677ed184242dd2a41875022027a aa54da28e36a3e91b4da2706c3896bdddef3286dbe51a06f7e53cad04e63b01",
                "hex" : "47304402203ed3b29bdfcc1a7e55e635b855605110c540c0d8f2d2677ed184242dd2a4187502202 7aaa54da28e36a3e91b4da2706c3896bdddef3286dbe51a06f7e53cad04e63b01"
            },
            "sequence" : 4294967295
        }
    ],
    "vout" : [
        {
            "value" : 0.00000000,
            "n" : 0,
            "scriptPubKey" : {
                "asm" : "",
                "type" : "nonstandard"
            }
        },
        {
            "value" : 21.42000000,
            "n" : 1,
            "scriptPubKey" : {
                "asm" : "036ed01fdf7a5b4cacbc938a6848cce2692501d8fe997e3e42eda372638ffa3864 OP_CHECKSIG",
                "reqSigs" : 1,
                "type" : "pubkey",
                "addresses" : [
                    "4bZaUMfgS43TtXqjzPPdq9yGmPBqWpL5wu"
                ]
            }
        },
        {
            "value" : 21.43966100,
            "n" : 2,
            "scriptPubKey" : {
                "asm" : "036ed01fdf7a5b4cacbc938a6848cce2692501d8fe997e3e42eda372638ffa3864 OP_CHECKSIG",
                "reqSigs" : 1,
                "type" : "pubkey",
                "addresses" : [
                    "4bZaUMfgS43TtXqjzPPdq9yGmPBqWpL5wu"
                ]
            }
        }
    ],
    "blockhash" : "e74de7bdc3d942f6a62b1d57c748699eafd46a4b867867460bc96a8fb6e76cec",
    "confirmations" : 1
}
alex@alex-VirtualBox:~/novacoin/src$

This hash should be identical for all possible modifications of transaction.