It's certainly not price stability, I can tell you that much.

A faster first confirmation is an enormous benefit if we want alternative currencies to be used in brick and mortar stores and restaurants. You can't have each person in line waiting 10 minutes or more.

You aren't going to have them wait 2.5 minutes (which may be up to 5x as long due to random nature block solutions) either.
So either payments will be prepaid, will be off blockchain. or the merchant will accept the low but non zero risk of double spend fraud.

When you consider the reduced security due to increased orphans and smaller overall network what exactly is the innovation.  Now you may be right something "significantly" superior to Bitcoin may replace it but that significantly superior solution isn't LTC and the horde of copy cat pump and dump scamcoins don't even have enough momentum to break out of a paper bag.

I've found out about Bitcoin in summer 2011. At once I undestood huge price growth potential of bitcoin. At the same time I was expecting something significantly better to emerge. I was even supporting some altcoins such as SC and LTC when they came out. But gradually I was learning more and more about how bitcoin works and what is difference between e.g. BTC and LTC. Several months after LTC release it was already clear for me, that all present alts offer nearly nothing new. And spread of their adoption can lead only to collapse of crypocurrencies in general.
One exception is PPC, they brought a new way of securing blockchain. So, for me it's the only credible altcoin.
Another new promising thing is zerocoin (it's even not an altcoin). IMO it incarnates what an alt should be. Although it doesn't look ready for widespread use, it shows the way. And makes today alts laughable.

Yeah that isn't a solution.  So the attacker simply DDOS the centralized point (or few points) of failure.

Still you seem to gloss over the fact that validating a block takes a non zero time.  Most of the delay isn't actual propogation delay it is validation delay.


For example time zero your node is notified (either directly or through so easy to take down centralized MBR what has to happen before you validate the block and begin work on a new one.

1 ) You must receive the list of transactions in the block (this could be modified to a list of tx hashes to be more efficient)
1a) If protocol sends tx hashes you will need to query peers for missing txs.
2 ) You must validate that each tx is valid which means
a) the inputs are unspent outputs (lookup/locate the referenced prior tx output in the UXTO)
 b) the tx is properly formed. no invalid structure, parsing issues.
 c) pub key for each input matches the pubkey hash of the prior unspent output (i.e. hash the pubkey and match to prior output pubkey hash)
d) for each input compute the simplifed tx form, the simplified tx hash and validate the signature.  
 e) verify that the sum of inputs exceeds the sum of the outputs.  note the difference between sum of inputs and outputs.
 f) parse and verify the tx output script is valid.
3 ) compute the merkle tree and merkle root hash (which involves 2n-1 hashes)
4 ) validate the coinbase value is correct (coinbase should be <= computed subsidy based on blockheight + sum of all tx fees in 2a)
5 ) validate the timestamp is within 2 hours of mean network time.
6 ) validate the prior blockhash in header refers to a known block
6a) if prior blockhash is unknown query peers for the block in question (and perform all the steps in this process on that block)
7 ) validate that difficulty & version is correct
8 ) compute blockhash and ensure it meets difficulty target

Even given infinite bandwidth and all miners having all other miners as a peer, this process takes a non-zero amount of time.  The most time sensitive elements are indicated in bold.  The single largest by time is the validating of all input tx signatures due to the fact that it is 1 ECDSA sig validation (relatively slow process) per input in the block. 

Today with relatively low tx volume the time to validate a block is sub 1 second but as block sizes grow (think hundreds of MB and hundreds of thousands or millions of transactions) that time will rise.

Now there are some optimizations possible but propogation delays will cause increased orphan rates in the future if network volume rises even to PayPal levels (50 to 100 tps).  A smaller block interval is going to result in higher orphan rates and less security.    Why do you think Satoshi decided on 10 minutes, why not 1 minute, or 1 seconds.  It never occurred to him that smaller block intervals would be possible?  Alt-coin "designers" simply modified the code thinking shorter = better but it is compromise.   Now I am not saying Bitcoin is perfect but any block interval is a compromise between Latency and security.
 

None of the alt coins have ANY advantages over bitcoin, and I'd say that most of them have serious disadvantages. An alt coin would only be worth using if it had a serious advantage over bitcoin and none do. Bitcoin was there first and that means a lot in this world.

Litecoin's faster confirmation time is actually a disadvantage as it doesn't do much aid in in-person store transaction and it results in a less secure blockchain.
Scrypt is only useful in that it isn't what bitcoin uses so there are no ASICs for it yet. If litecoin was actually useful we'd see ASICs designed for scrypt and on the market in months and litecoin mining would essentially be the same as bitcoin mining. There reason why there are no litecoin ASICs is because the market is far too small for any designers to give a damn.

Bitcoin does not need a "silver" to it's "gold". Bitcoin is divisible to 100 million pieces and doesn't "silver". I don't really get what people mean by that analogy anyways. To me it sounds like: here is Bitcoin, it is like gold. Or you have use Litecoin instead, which is like Bitcoins crippled step-brother that no one uses, isn't accepted anywhere, and isn't really as good. You can have that instead if you like. Why would anyone chose Litecoin over Bitcoin?

Yeah I don't think you understand how modern DDOS work.  The attacker hits your upstream provider with hundreds of GB/s of traffic, the simply null route you to deal with the flood.  It is why DDOS are so hard to deal with.  The pipe to your server simply becomes saturated beyond your bandwidth capabilities.  You can't filter our the good nodes if they can't get to your server.

The idea that you know all miners so you can whitelist them is somewhat disconcerting as well.  You have essentially created the central mining agency.  The entity which all miners must work with to have any chance at efficient mining.  Not really sure that is the "solution" as opposed to simply using a more efficient (large) block interval.


Even at 10MB we are talking, a not so insignificant delay.  

Still lets assume for a second you overcome the philosophical and vulnerability issues of a centralized clearing house. This still means a 2 hop propogation delay.  

The critical window = (time to transmit to clearing house) + (time for clearing house to validate block) + (time to transmit to other miners) + (time for other miners to validate)

Today validating a 500 KB block can take upwards of 300 ms.  10MB would be more like 6000 ms.  Lets assume protocol efficiencies cut that in half say 3000 ms.  Remember there are two validations unless miners are just going to blindly (100% implicit trust) the data provided by the clearing house.  Say the clearing house has 100 Mbps synchronous lot latency connectivity.  The transmit time from miner to clearing house then becomes 5*8/100 = 0.4 seconds.  If there are (a guess) 50 miners using the clearing house the time to transmit to the miners is another 50*10*8/100 = 40 seconds.

Under this naively optimistic scenario we are talking 0.4 + 3+ 40 + 3 = 46.3 seconds for full validation and double hop propagation to 50 mining peers.  With Bitcoin's 600 second average block time this means an orphan rate of ~8%.  With LTC it is more like 26%.  With the idiotic 30 second block intervals used by some scamcoins it is something on the order of 80% orphans.

Now there are solutions to make block propagation more efficient.  One (not possible on Bitcoin but could be used on an altcoin) would be to use a simplified transaction structure.  I have done some modeling and see a roughly 60% reduction in block size is possible (i.e. 1.7x as many tx in the same sized block).  For Bitcoin/Litecoin a soft fork where block is separated into header and tx set would allow more efficient pre-propogation of transactions.  Still at the end of the day smaller block intervals are going to face scaling challenges much quicker and an increased loss of security due to orphans is inevitable.

We have computers that will smoke anything you can throw at us the Chinese are just spinning their wheels on this one..Ira

Alt coins not only have no advantage over Bitcoin, they actually deteriorate the chance of crytocurrencies in general being successful. More cryptocurrencies at an early stage lead to pseudo-inflation to an extent, destabalising the price, leading to further volatility, leading to merchants getting turned off. Its not the only cause of volatility but in an extreme scenario with multiple coins being actually accepted at the same time (currently bitcoin is the only one really accepted) then it has the potential to. At a later stage when bitcoin is established this isn't really much of a threat.

The only altcoin I really have respect for is namecoin, because it builds in 'intrinsic value' into the coin, something which Bitcoin actually lacks and could use. Otherwise all the other altcoins are seriously retarded.