1) Can someone explain to me how to check if a bitcoin address contains only fresh mined bitcoins?
It depends on your level of technical knowledge.
You could just look the address up on a block explorer. For example, if you search for the address 1J6Ar4Kw4iQotPXAq9wVpFzFjpwBnppHjd at blockchain.info you'll discover that it has only ever received 1 transaction, and that transaction looks like this on their website:
If all the transactions that have ever been sent to the address all indicate "No Inputs (Newly Generated Coins)" at blockchain.info, then the address has only ever contained "freshly mined bitcoins".
If you are writing software that is capturing bitcoin transactions directly from the bitcoin network, and attempting to determine if the transaction is creating "freshly mined bitcoins", then you'll need to look at the broadcast blocks. Transactions that create newly mined bitcoins are not sent on the network unless they included as part of a mined block. It will always be the first transaction in the block, and it will look like this:
decoderawtransaction 01000000010000000000000000000000000000000000000000000000000000000000000000ffffffff0804ffff001d02db00ffffffff0100f2052a0100000043410415cf72a1f6afb54376d751647b22b78d53f6ff01bacf47082d255fa69905194d621675dd6421027e4d79153ad0b1283ed0b5e3e728f98efb3bddbfd0b52e4203ac00000000
{
"txid" : "866eb68a77bd457c3c0dab400b948aa911effce03e4700fa49857f46f6091cef",
"version" : 1,
"locktime" : 0,
"vin" : [
{
"coinbase" : "04ffff001d02db00",
"sequence" : 4294967295
}
],
"vout" : [
{
"value" : 50.00000000,
"n" : 0,
"scriptPubKey" : {
"asm" : "0415cf72a1f6afb54376d751647b22b78d53f6ff01bacf47082d255fa69905194d621675dd6421027e4d79153ad0b1283ed0b5e3e728f98efb3bddbfd0b52e4203 OP_CHECKSIG",
"hex" : "410415cf72a1f6afb54376d751647b22b78d53f6ff01bacf47082d255fa69905194d621675dd6421027e4d79153ad0b1283ed0b5e3e728f98efb3bddbfd0b52e4203ac",
"reqSigs" : 1,
"type" : "pubkey",
"addresses" : [
"1J6Ar4Kw4iQotPXAq9wVpFzFjpwBnppHjd"
]
}
}
]
}
Notice the lack of "txid", "vout", and "scriptSig" in the "vin".
There are only 2 ways to check what a bitcoin address "contains". One is to scan the blockchain and process all transactions that have ever been sent to that address keeping track of which outputs have been spent, and the other is to use a service (either one you've created, or one provided by a third party) that has already done that and request the information from the service.
2) Fresh bitcoins don't have any previous ownership?
Correct.
Are they just in one address without a trail to it?
They are just 1 transaction without a trail to it. It could be one address. It could be multiple addresses. There could be a trail to the address from other transactions. If you are asking technical questions, then it is very important to understand that at the protocol level,
BITCOIN DOES NOT WORK THE WAY YOU ASSUME IT WORKS. The protocol doesn't know anything about "addresses". It doesn't know anything about "balances". There are only "inputs" and "outputs". Inputs are always specifically identified previously unspent "outputs". Outputs are always a value that has been encumbered with a requirement that must be met to be allowed to use that output as an input.
3) Do pools give out only bitcoins from the bitcoin reward or you can expect to get bitcoins which have been mined some time before?
It depends on the pool. A pool can get the bitcoins that they give as a reward from anywhere they like, as long as the pool participants agree or don't care.
4) Can someone provide an example address which contains fresh bitcoins?
1J6Ar4Kw4iQotPXAq9wVpFzFjpwBnppHjd
