Which is the reliability of a transaction timestamp?

Question

Just one question. Where and how is the TIMESTAMP of a transaction generated?

Is it reliable to develop a transactions notification system?

Thank you! (I mean the time node below)

{ "hash":"44ffca26a089ccc806a7861e715d237d9f63b373085492f2ee82901171e8d661", "ver":1, "vin_sz":1, "vout_sz":2, "size":257, "relayed_by":"127.0.0.1", "tx_index":31066681,"result":0, "time":1351624745,"block_height":205754, "inputs":[ { "prev_out":{ "type":0, "addr":"1PAPY4UN1NtFwRibWRuFT1CkgK3NvnMpoC",
"value":879000000, "tx_index":31055718, "n":1 } } ], "out":[ { "addr":"1ELop4RiQtsVnqPJZHqErCvmJZPHsVn2YT", "value":5000000, "type":0 } ,{ "addr":"1PAPY4UN1NtFwRibWRuFT1CkgK3NvnMpoC",
"value":874000000, "type":0 } ] },

Answer 1

The timestamp is not a part of the standard transaction as per Bitcoin Protocol Specification. It is most likely generated by the standard client during the api call. The standard client might use its internal time (that might differ from the machine time), which is vulnerable to timejacking. I might be wrong, however.

As long as your client is running properly, it should be okay to use its timestamps for various notifications. They might represent the time the client received the transaction however, which may differ from the time the transaction was broadcast the first time.

Answer 2

"Is it reliable to develop a transactions notification system?"

this is already existing, you could be interested in looking at :

https://github.com/MORA99/BitPing.Net

afaik you dont really need the timestamp to do that, but just use a block explorer like abe : http://github.com/jtobey/bitcoin-abe

and your application will be notified of any new transaction