I have trouble implementing parallel blockchain download (headers only). I read wiki back and forth, but do not understand:
1) What exactly is block locator object.
2) How to download headers before certain block (towards genesis block)
Now I can start from genesis and work up blockchain (using 0 as hash_stop). Is it possible to move in opposite direction (from newest blocks to genesis)?

http://www.securelist.com/en/blog/208194206/An_avalanche_in_Skype

There is a new malicious ongoing campaign on Skype. It’s active and kicking yet.
The infection vector is via social engineering abusing infected Skype by sending massive messages to the contacts like these ones:
i don't think i will ever sleep again after seeing this photo http://www.goo.gl/XXXXX?image=IMG0540250-JPG
tell me what you think of this picture i edited http://www.goo.gl/XXXXX?image=IMG0540250-JPG
<snip>
Finally something interesting is this:

And similar malware spreads bitcoin miner:
http://www.securelist.com/en/blog/208194210/Skypemageddon_by_bitcoining

So what does malware do? To be honest many things but one of the most interesting is it turns the infected machine to a slave of the bitcoin generator. The usage of CPU grows up significantly. Here is an example:

The mentioned process runs with the command ?bitcoin-miner.exe -a 60 -l no -o http://suppp.cantvenlinea.biz:1942/ -u XXXXXX0000001@gmail.com -p XXXXXXXX� (sensitive data was replaced by XXXXXX) It abuses the CPU of infected machine to mine Bitcoins for the criminal.

Are transaction IDs (32-byte hashes of TX body) on blockchain.info written backwards, i.e. with bytes reversed?
Or it's mistake on my end, and I have it backwards myself?

I was interested, how fast do transactions propagate through network in reality?
I was thinking, if I can connect to every node and listen to inv messages, I could estimate it (node should send inv when it got tx and verified it, and only once). Well, I did exactly that. Only I ended up connected not to all nodes, but to fair share of them (~1900 active connections at the end of the experiment). I logged every inv message with timestamp. After several hours, I processed resulting 2.5 Gb text file with python, remembering time I first saw each transacion hash, and next time I got inv with it, I calculated time difference, binning it (used 1 sec bins) and summing over all transactions.
I ended up with following distribution (x is in seconds):

What can I say? Certainly, propagation speed is not that great. "Tails" are quite long. There are fair amount of retransmits (I believe second mode is result retransmits).
Please discuss.

Hello all!
For some time I was working on bitcoin daemon implementation in erlang.
Now it's in the early stage of development. I'm trying to implement protocol not looking into bitcoind source, but using specification from https://en.bitcoin.it/wiki (found one bug so far), original paper and looking at the protocol messages which I get from peers.

My goal is to make scalable bitcoin daemon, capable of serving many thousands of peers on relatively low-end servers.
At current state it's capable of connecting and parsing messages from 3000+ peers on 256M RAM VPS without swap. It does not do much besides protocol parsing and peer discovery now, but it's only several days old. Chances are that it connected to your machine - check for /ebtcd:0.0.1/ user-agent in logs.
Short term pans: accept incoming connections, announce own address via addr message.
Mid term plans: add validation and routing (test on testnet), release source under open license (AGPL sounds good).
Long term: full-featured daemon.

P.S. In case someone wants to encourage me with some BTC, I set up donation adress:
1GVmS56pvVL7YZA7YqMBXmaDedCoputKuJ

UPD:
git clone git://github.com/r-willis/biten.git

Hello all!
For some time I was working on bitcoin daemon implementation in erlang.
Now it's in the early stage of development. I'm trying to implement protocol not looking into bitcoind source, but using specification from https://en.bitcoin.it/wiki (found one bug so far), original paper and looking at the protocol messages which I get from peers.

My goal is to make scalable bitcoin daemon, capable of serving many thousands of peers on relatively low-end servers.
At current state it's capable of connecting and parsing messages from 3000+ peers on 256M RAM VPS without swap. It does not do much besides protocol parsing and peer discovery now, but it's only several days old. Chances are that it connected to your machine - check for /ebtcd:0.0.1/ user-agent in logs.
Short term pans: accept incoming connections, announce own address via addr message.
Mid term plans: add validation and routing (test on testnet), release source under open license (AGPL sounds good).
Long term: full-featured daemon.

P.S. In case someone wants to encourage me with some BTC, I set up donation adress:
1GVmS56pvVL7YZA7YqMBXmaDedCoputKuJ