51% attack

[Blimpo]

What will happen to Bitcoin if a major coin like Litecoin suffers a 51 % attack?

[beatljuice]

Not much. Unless the media somehow gets a hold of the news and blows it all out of proportion as they tend to do.

[Pobre]

Well if ltc suffers from 51% , i think the ltc value may go downto a few cents, now answering your question that what will happen to btc, i think two things are possible- 1. as ltc suffers btc will gain, because altcoins damage the btc prices, so when ltc will loose value, btc will go up in price.
2. the second thing that can happen is that the people may also start fearing about a 51% attack on btc too, and this will make the btc loose.

[WheresWaldo]

What will happen to Bitcoin if a major coin like Litecoin suffers a 51 % attack?

Explain this 51% attack you speak of 

[shorena]

What will happen to Bitcoin if a major coin like Litecoin suffers a 51 % attack?

Explain this 51% attack you speak of 

A 51% attack is usually understood as a person or group (lets call he/she/them A) having 51% of the available hashing power. Most cryptocurrencies work with a blockchain where the longest chain is the valid one. So if you make a transaction and spend 10 LTC/BTC/whatevercoin but have the hashing power to revert this transaction by making a new longer chain that does not include said transaction, you can double spend coins. A could spend coins everywhere and when A got what was paid for, just "revoke" the coins, which usually is not possible. Even with 51% it is not allways possible. Finding a block is allways also a matter of chance and not only of pure hashingpower. With every "legit" block you have to find another "malicous" block. But there have been small (low overall hashingpower) altcoins that have been destroyed this way. Some big miners even consider it a good deed to destroy "pump and dump" coins.
With "the big" coins there is a major argument against a possible 51% attack. This would devalue the coin and thus reduce the usefullness. Think about the money youd have to spend to gather 51% of the Bitcoin hashingpower. This "investment" would probably never pay off.
Overall I dont think that any major coin will suffer a 51% attack any time soon.

[b!z]

Who cares about other altcoins?

Their economies rely on bitcoin. It's not the other way around.

[b!z]

What will happen to Bitcoin if a major coin like Litecoin suffers a 51 % attack?

Explain this 51% attack you speak of 

A 51% attack is usually understood as a person or group (lets call he/she/them A) having 51% of the available hashing power.

Technically, it's a >50% attack, not a 51% attack.

http://bitcoin.stackexchange.com/questions/10936/is-it-a-51-attack-or-a-50-attack

[jkljb]

The Hash Rate is approaching of 51%, what can happen if this occurs?

They could launch a 'Timewarp attack', but LTC's fast block times makes this much harder and impractical to succed compared to BTC.

But BTC is also not immune to attacks like: https://bitcointalk.org/index.php?topic=67900.msg790683#msg790683

[rajko00]

How much procent cex.io have?

[icet208]

The Hash Rate is approaching of 51%, what can happen if this occurs?

They could launch a 'Timewarp attack', but LTC's fast block times makes this much harder and impractical to succed compared to BTC.

But BTC is also not immune to attacks like: https://bitcointalk.org/index.php?topic=67900.msg790683#msg790683

that's an old chart..now ghash.io has around 35% of the network..51 attack it`s not a real problem

[Soappa]

What will happen to Bitcoin if a major coin like Litecoin suffers a 51 % attack?

Explain this 51% attack you speak of 

A 51% attack is usually understood as a person or group (lets call he/she/them A) having 51% of the available hashing power.

Technically, it's a >50% attack, not a 51% attack.

http://bitcoin.stackexchange.com/questions/10936/is-it-a-51-attack-or-a-50-attack

Indeed, the most hashrate you have, the more likely the attack will be successful.
It is possible to launch a so-called "51% attack" with 40% network hashrate, but with a much lower success rate.

FYR: https://en.bitcoin.it/wiki/Weaknesses#Attacker_has_a_lot_of_computing_power

Attacker has a lot of computing power

An attacker that controls more than 50% of the network's computing power can, for the time that he is in control, exclude and modify the ordering of transactions. This allows him to:

    Reverse transactions that he sends while he's in control. This has the potential to double-spend transactions that previously had already been seen in the block chain.
    Prevent some or all transactions from gaining any confirmations
    Prevent some or all other miners from mining any valid blocks

The attacker can't:

    Reverse other people's transactions
    Prevent transactions from being sent at all (they'll show as 0/unconfirmed)
    Change the number of coins generated per block
    Create coins out of thin air
    Send coins that never belonged to him

With less than 50%, the same kind of attacks are possible, but with less than 100% rate of success. For example, someone with only 40% of the network computing power can overcome a 6-deep confirmed transaction with a 50% success rate.

[Velkro]

ghash.io also has around 40% now on bitcoin, but to do attack with it, they would loose more that they could gain by me

[Soappa]

ghash.io also has around 40% now on bitcoin, but to do attack with it, they would loose more that they could gain by me

AFAIK, Ghash is still quite a bit short of 40%.

It solves 35% of blocks for the past 4 days. (https://blockchain.info/pools?timespan=4days)
It solves 32% of blocks for last week, from May18 to May24. (http://organofcorti.blogspot.com/search/label/weeklypoolstatistics)
It solves 33.5% for the past 2016 blocks. (http://blockorigin.pfoe.be/top.php)

[LiteCoinUser84]

a 51% attack on LTC imo would actually increase BTC value since people mining BTC would realise its danger after LTC drops like a sack of cr*p and would lead to more careful mining of BTC. Value might increase.

[shorena]

ghash.io also has around 40% now on bitcoin, but to do attack with it, they would loose more that they could gain by me

AFAIK, Ghash is still quite a bit short of 40%.

It solves 35% of blocks for the past 4 days. (https://blockchain.info/pools?timespan=4days)
It solves 32% of blocks for last week, from May18 to May24. (http://organofcorti.blogspot.com/search/label/weeklypoolstatistics)
It solves 33.5% for the past 2016 blocks. (http://blockorigin.pfoe.be/top.php)

Keep in mind that GHash is still a pool. ~55% of their hashing power is from indipendend miners¹. They could be gone very fast if word gets out that GHash is attacking the network.

Technically, it's a >50% attack, not a 51% attack.

http://bitcoin.stackexchange.com/questions/10936/is-it-a-51-attack-or-a-50-attack

I should have been more precise, thanks for the correction.


1 https://ghash.io/ghashio_press_release.pdf

[jkljb]

~snip~

They could launch a 'Timewarp attack', but LTC's fast block times makes this much harder and impractical to succed compared to BTC.

But BTC is also not immune to attacks like: https://bitcointalk.org/index.php?topic=67900.msg790683#msg790683

that's an old chart..now ghash.io has around 35% of the network..51 attack it`s not a real problem

This is graph of LTC Network