The Anatomy of a Transaction

A transaction in IOTA consists of 2673 trytes (if encoded). When you decode the trytes you get a transaction object which has the following values:

• hash: String 81-trytes unique hash of this transaction
• signatureMessageFragment : String 2187-trytes signature message fragment. In case there is a spent input, the signature of the private key is stored here. If no signature is required, it is empty (all 9's) and can be used for storing the message value when making a transfer. More to that later.
• address: String 81-trytes address. In case this is an *output*, then this is the address of the recipient. In case it is an *input*, then it is the address of the input which is used to send the tokens from (i.e. address generated from the private key)
• value : Int value transferred in this transaction
• timestamp : Int timestamp of the transaction. It is important to know that timestamps in IOTA are not enforced.
• currentIndex : Int the index of this transaction in the bundle.
• lastIndex : Int the total number of transactions in this bundle
• bundle: String81-tryte bundle hash, which is used for grouping transactions of the bundle together. With the bundle hash you can identify transactions which were in the same bundle.
• trunkTransaction : String 81-trytes hash of the first transaction that was approved with this transaction
• branchTransaction: String 81-trytes hash of the second transaction that was approved with this transaction
• nonce: String 81-trytes hash. The nonce is required for the transaction to be accepted by the network. It is generated by doing Proof of Work (either in IRI via the attachToTangle API call, or with one of the libraries such as ccurl).

The core clients encode all of this data into trytes and store it as a string of 2673-trytes. In order to read this data, you will have to decode / encode it with the client library functions. Here is an example of what such a transaction in raw trytes format looks like:

999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999A9RGRKVGWMWMKOLVMDFWJUHNUNYWZTJADGGPZGXNLERLXYWJE9WQHWWBMCPZMVVMJUMWWBLZLNMLDCGDJ999999999999999999999999999999999999999999999999999999YGYQIVD99999999999999999999TXEFLKNPJRBYZPORHZU9CEMFIFVVQBUSTDGSJCZMBTZCDTTJVUFPTCCVHHORPMGCURKTH9VGJIXUQJVHK999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999

And here is the same transaction object (you can try and convert this yourself, with `iota.utils.transactionObject()`):

{
    "hash":"IPQYUNLDGKCLJVEJGVVISSQYVDJJWOXCW9RZXIDFKMBXDVZDXFBZNZJKBSTIMBKAXHFTGETEIPTZGNTJK",
    "signatureMessageFragment":"999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999",
    "address":"A9RGRKVGWMWMKOLVMDFWJUHNUNYWZTJADGGPZGXNLERLXYWJE9WQHWWBMCPZMVVMJUMWWBLZLNMLDCGDJ",
    "value":0,
    "tag":"999999999999999999999999999",
    "timestamp":1482522289,
    "currentIndex":0,
    "lastIndex":0,
    "bundle":"TXEFLKNPJRBYZPORHZU9CEMFIFVVQBUSTDGSJCZMBTZCDTTJVUFPTCCVHHORPMGCURKTH9VGJIXUQJVHK",
    "trunkTransaction":"999999999999999999999999999999999999999999999999999999999999999999999999999999999",
    "branchTransaction":"999999999999999999999999999999999999999999999999999999999999999999999999999999999",
    "nonce":"999999999999999999999999999999999999999999999999999999999999999999999999999999999"
}