problem with bitcoin payment fees

[RexBrocki]

Wow.  I post a simple question, look at the first few replies, go take a nap and then come back and see a plethora of knowledgeable replies on the topic from the bitcoin community.

As I said, wow.

This confirms me in the belief, formed over a year ago, that for some reason, bitcoin has sucked in some of the brightest people on this planet.

That having been said, however, now I REALLY think there's a bug in this wallet.  I was already aware (though not to the depth that many of the people replying to my post are, to be sure) of the age and "dust" issues... but that still doesn't explain why the fees my wallet is requesting change at every request, EVEN WHEN I'M NOT CHANGING ANYTHING ELSE.

Other data: there are only two transactions in this wallet younger than EIGHT MONTHS.  This was one of my first wallets, set up over a year ago, when I was first getting into bitcoins, and I was just trying to clean up and remove any coins from this old wallet before May 15th and shut off the POS laptop it occupies.

The two newest transaction are also over two weeks old, two referrals from Bitvisitor for 8 and 16 microbitcoins respectively... these are also the two smallest transactions in the wallet, as far as I am aware.  Every other transaction is at least seven and a half months older and up into the milli-bitcoin range or larger.

Thanks everyone for the cogent replies... and if anybody can figure out how the requested fees can jump around like a flea with an itch, pray continue.

[Birdy]

Thanks everyone for the cogent replies... and if anybody can figure out how the requested fees can jump around like a flea with an itch, pray continue.

My guess is that the used coins for the transaction are selected randomly.
Usually you have to pay a size fee for every 5-6 transaction used, so if it selects 30 dust transactions...
The age of the coins isn't relevant to this fee.

There are two different fees, one is about the file size (0.0005 for every 5-6 transactions included),
the other one is about priority (fixed 0.0005).


Btw:
The formula for priority is
priority = ((BTC address balance*100000000) * number of confirmations (weighted over all coins) / size of transaction message in bytes)
A priority of 57.600.000 is needed to send without fees.
It will be years before you could send dust without fee without bundling it with bigger transactions.

This is mandatory in the qt-client, the fees aren't enforced by the Bitcoin system itself.
So it could be handled in another way by the online wallet.

[alyssa85]

Btw:
The formula for priority is
priority = ((BTC address balance*100000000) * number of confirmations (weighted over all coins) / size of transaction message in bytes)
A priority of 57.600.000 is needed to send without fees.
It will be years before you could send dust without fee without bundling it with bigger transactions.

Hi - I just checked on my blockchain wallet - the oldest transaction has over 900 confirmations. How high do the confirmations go? Does anyone have any idea?

[DannyHamilton]

- snip -
Hi - I just checked on my blockchain wallet - the oldest transaction has over 900 confirmations. How high do the confirmations go? Does anyone have any idea?

They don't stop.  Every time a new block is added to the blockchain (approximately every 10 minutes on average), the transaction is considered to have another "confirmation".  This will continue for as long as bitcoin exists.

[alyssa85]

OK - another question about inputs and outputs.

Say I have a wallet with 2 BTC in it, which is made up of 50inputs of  0.04BTC each. I want to send 1BTC to another wallet - am I right that this will be made up of 25 inputs, and the transaction size will be 25 x 200bytes = 5000 ?

[DannyHamilton]

OK - another question about inputs and outputs.

Say I have a wallet with 2 BTC in it, which is made up of 50inputs of  0.04BTC each. I want to send 1BTC to another wallet - am I right that this will be made up of 25 inputs, and the transaction size will be 25 x 200bytes = 5000 ?

Yes, if every unspent output in your wallet was exactly 0.04 BTC, then a transaction to send 1 BTC would be at least 25 inputs.  Depending on the wallet program used to create the transaction there might be a preference programmed in to create "change".  This improves privacy a bit.  If a transaction only has a single output, then it becomes immediately obvious what address is being paid and how much is being sent.  If an address has 2 outputs, then it isn't as easy for someone to tell which is the "change" and which is the "payment".  If the wallet has a preference programmed in to create "change", then it might actually use something like 28 inputs, and create a second output for 0.12 BTC.


A transaction size is made up of more than just inputs, and inputs are typically more like 180 bytes each.

For the sake of the math, lets assume that your wallet creates a transaction with exactly 25 inputs and 1 output, here's the structure of such a transaction:

Code:

4 byte version number
1 byte input quantity

Then for each input:

Code:

32 byte transactionID
4 byte index
1 byte scriptSig length
1 byte signature length
variable length signature (perhaps typically approximately 72 bytes?)
1 byte public key length
65 byte public key
4 byte sequence number

(That's 108 bytes plus the signature per input, figure a typical input at 180 bytes)
Then:

Code:

1 byte output quantity

Then for each output:

Code:

8 byte output value
1 byte script length
1 byte OP_DUP script code
1 byte OP_HASH160 script code
1 byte code to push 20 bytes onto the script processing stack
20 byte bitcoin address to pay to
1 byte OP_EQUALVERIFY script code
1 byte OP_CHECKSIG script code

(That's 34 bytes per output)


So depending on the length of the signatures in your example transaction, it should be around:

4 + 1 + (180 X 25) + 1 + (34 X 1) = 4,540 bytes

[alyssa85]

DannyHamilton - you're a star! Thank you very much!