You probably want to move this here:

https://bitcointalk.org/index.php?board=99.0

But it isn't the real private key, he has replaced part of the key:
 5hutyAewDs9BsUqVh1Nivythf49VvEzGXpDYj37ZLtDxdDyXN7D

Hence the " 44/51 or ~86% (assuming 7 hidden and 51 total)" comment by shorena.

It is more of a security by obscurity argument to transform a portion of the key.  It isn't a valid key of course with the substitutions.  

If you are looking for a private key that has a replaceable prefix it decreases the search space dramatically and isn't safe.

edit:  You can obviously do as you wish, but be very careful and be sure to understand the ramifications of what you are doing. 

One option is to just generate them in bulk - e.g. 50000 at a time on a different computer with bitcoin core or something - and then just reference the public keys from php.  Marking them as used as you go along (so you don't reuse them).   This also avoid exposing the private key to a web connected machine which could be considered a security risk.

You can also use bitcoin core as a backend and generate them there using php.  

It is difficult to code your own correctly due to the ease of introducing bugs (e.g. in the PRNG or elsewhere).  Sometimes it is more efficient and safer to use code that has been well tested.

1. Anonymity - of you and everyone you transact with is improved.
2. It wasn't mentioned above, but re-use can impact security - one you "spend from" an address you have "released" your "public key" into the wild (prior to that only the Base58 encoded RIPEMD hash of it (the "address") was publicly known ).  If ECDSA is broken (or the implementation is fragile) your coins are secure if you haven't reused addresses. 
3. Related to #2, without reuse bitcoin is more quantum computer resistant so your coins are better protected.

Since 0.10.0 there is no need to sync via torrent due to the headers first sync.  If you read the thread above (among many other threads and discussions about this) and understand it, it wouldn't improve performance, just add something that isn't needed.

However, if you think it is a good idea for whatever reason, it is something that you can implement and then see if it improves anything or just adds complication. 

Also, how long have you left it running?  Give it some time.

Yeah, cloud servers for bitcoin (or other financial) web sites are prone to issues.

Of course if you were to buy a Dell (at least laptop), you'd have to worry about self-signed root certs, so it seems that there are holes everywhere...no comfort there.

See: http://www.techweekeurope.co.uk/security/firewall/superfish-like-rogue-certificates-found-pre-installed-dell-pcs-181034

You might ask in the electrum forum, but that said, at least export the private keys so you'll have a backup.

I think he was asking why double hashing vs just a single sha256.

If so, it was to help prevent length-extension attacks:

see e.g.
http://crypto.stackexchange.com/a/884

There are 2^160 addresses, the sun will expire before bitcoin "runs out" of addresses.

It is best practices to not re-use addresses, but people are free to do as they wish.  Some places may require a new one, others may not.

Are you sure that port forwarding is working properly?  e.g. forwarding port 8333 from the router to port 8333 on your internal machine? 

Can you connect to the admin control panel on the 2wire modem?  Many of the 2wires have a firewall built in which could be (and probably is) blocking that port.  (It's login page should be something like one of these.  If you know your internal IP address of the computer, that will give a hint: 10.0.0.138, 192.168.0.1,192.168.1.0 ,192.168.1.1, 192.168.1.254, gateway.2wire.net ,http://gateway.2Wire.net  )

You'll need the username and password for the router.  If you haven't changed them, it could be both blank for both or "admin" and "2wire" (or "Wireless")...varies.

Then in there, you'd need to look for the port forwarding section and update that.  If you put a router in between the modem and the computer, you'd need to set it up there too.

You'd want the 2wire (and router if you have on there too) to say something like allow all incoming connections from the WAN on port 8333 to go to port 8333 on the internal IP address (e.g. something like 192.168.1.55 -- whatever the local IP of the bitcoin server is, you'd want to set that to something static and not use DHCP to set the IP for that machine.  And assuming you are still on 8333.)



Once you check that, if you use a tool like this:
http://www.yougetsignal.com/tools/open-ports/

It should show that it is open if forward is working so that it connects to your local computer.  Bitnodes gives similar info, but will check not just the port.  If the port gets opened, then bitnodes should show it working too.

If you have another machine on your local network, can you check and see from that machine if port 8333 is accessible?  I bet it is, but if not, then it could be the firewall on the machine vs on the modem.

:-)

With headers first, Bitcoin Core can sync through multiple nodes (0.10.0 and up).

As a test, if you go here:
https://bitnodes.21.co

where it says "Join the Network" and enter your IP, does it show that you are accepting connections from other nodes?

Are you unreachable or reachable? 

Does the transaction show up in your balance?  Does the address show up in Bitcoin Core? If so, you should be able to export the private key.  If not, you should be able to recover it from a backup of the wallet.

If you are running the same code as you were in the past with no problems, then sure.  If you are running 0.11.2, it is not the same as running 0.3.24, for example. 

Something to check.

And iirc, doesn't that only have 1GB of RAM?

This is off topic here.

But, without the transaction IDs, no one will be able to see what is going on.  

You should talk to "polo" - the shirt people?  - to see if they paid fees Etc.

If this is a huge concern, you should speak with someone in your country who is familiar with the relevant laws.

Did you give the person or entity that sent you the coins that address?  Are you saying you don't have the private key for it?

You could try something like monit to monitor it and restart it when needed.

If you mean a completely new server, that would be somewhat more complicated, but probably something like AWS' tools would be helpful, depending on your host.

Give it a try from the command line first, then you can see whether it is bitcoind or not:

e.g.

bitcoin-cli getinfo

Then, you might try

127.0.0.1

for the IP.