bitcoin version 1, addresses space 2^160

HeRetiK

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Quote from: crofrihosl on September 24, 2019, 07:33:20 AM

chose any public address with an output spent (must have at least one output transaction ) i will easy extract the public key Grin

i learned this few hours ago Tongue

Yes, that's because outgoing transactions from P2PKH addresses need to publish the public key as well, otherwise no one could verify that the transaction is valid. That's not "extracting the public key" that's merely parsing public information.

crofrihosl

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Quote from: HeRetiK on September 24, 2019, 03:06:32 AM

Quote from: crofrihosl on September 24, 2019, 12:09:05 AM

can we go address > public key ?

Whether the public key can be derived from a P2PKH address? No.

Quote from: pooya87 on September 24, 2019, 04:20:54 AM

Quote from: crofrihosl on September 24, 2019, 12:09:05 AM

Quote from: pooya87 on September 23, 2019, 11:01:43 PM

an address is the hash of the public key where as those outputs

can we go address > public key ?

no we can not go from address to public key

chose any public address with an output spent (must have at least one output transaction ) i will easy extract the public key Grin

i learned this few hours ago Tongue

pooya87

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Quote from: crofrihosl on September 24, 2019, 12:09:05 AM

Quote from: pooya87 on September 23, 2019, 11:01:43 PM

an address is the hash of the public key where as those outputs

i feel almost every words of you has some hidden meaning

can we go address > public key ?

what i meant was to point out that there is a difference between addresses and scripts. address is the human readable encoding of some of the most popular scripts, in other words we have more scripts than addresses. example is the P2PK scripts that were mentioned, another would be those with OP_CSV or other OP codes in them.

as for second part, no we can not go from address to public key since hash algorithms used in bitcoin are one way functions.

HeRetiK

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Quote from: crofrihosl on September 24, 2019, 12:09:05 AM

can we go address > public key ?

What do you mean? Whether the public key can be derived from a P2PKH address? No. The public key is cryptographically hashed, which means it's been put through a cryptographically secure one-way function that does not allow for an easy reversal of the process.

crofrihosl

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Quote from: pooya87 on September 23, 2019, 11:01:43 PM

an address is the hash of the public key where as those outputs

i feel almost every words of you has some hidden meaning

can we go address > public key ?

Code:

base58check({version byte}RIPEMD160(SHA256(pubkey)))

http://gobittest.appspot.com/Address

pooya87

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Quote from: crofrihosl on September 23, 2019, 12:58:41 PM

i have this question when exactly the year and month we start using 2^256?

the year that we succeed at optimizing the algorithm for nested hash function {RIPEMD160(SHA256)} and find a collision. nobody can predict when that can happen, estimating it would be at least another 50 years.

Quote from: crofrihosl on September 23, 2019, 03:01:32 PM

~
am i understand you correctly!
all bitcoin addresses use 2^160 160bits and the only exception 2009 and 2010 that use 2^256 Embarrassed

an address is the hash of the public key where as those outputs from first year(s) were the public key itself.

Quote from: ?? on ??

There's no change of "bitcoin version 1", assuming you're talking about Bitcoin address which have prefix 1.

Bech32 address format have more character count, but according to https://bitcoin.stackexchange.com/a/69554 it also uses RIPEMD-160 which means current address space is still 2^160, but only with different format/encoding. CMIIW.

P2WPKH scripts are using the same RIPEMD160(SHA256(pubkey)) digests so they are the same 20 bytes (160 bits). P2WSH scripts use SHA256(script) digest so they are 32 bytes (256 bits) and both of them use Bech32 encoding to represent the corresponding "address".

crofrihosl

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Quote from: aplistir on September 23, 2019, 01:54:33 PM

Bitcoin has almost always used address space of 2^160, and is still using it.

The only exception are those addresses that were created in 2009 (and 2010) --snip--

am i understand you correctly!
all bitcoin addresses use 2^160 160bits and the only exception 2009 and 2010 that use 2^256 Embarrassed

Quote from: ?? on ??

There's no change of "bitcoin version 1", assuming you're talking about Bitcoin address which have prefix 1.

Bech32 address format have more character count, but according to https://bitcoin.stackexchange.com/a/69554 it also uses RIPEMD-160 which means current address space is still 2^160, but only with different format/encoding. CMIIW.

not the prefix i meant the the address space ()
this line is clear something to me: There are exactly 2^160 possible addresses as long as we keep using RIPE-MD160.

old topic https://bitcointalksearch.org/topic/how-many-possibly-bitcoin-addresses-are-there-exactly-and-how-long-does-it-24268

aplistir

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Bitcoin has almost always used address space of 2^160, and is still using it.

The only exception are those addresses that were created in 2009 (and 2010), that did have and still have an address space of 2^256.
Those addresses are the P2PK addresses. (P2PK= "pay to public key")

P2PK addresses have address space of 2^256, because there is only one public key that corresponds to one private key.

crofrihosl

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i have this question when exactly the year and month we start using 2^256?
...
all addresses before 2013 use 2^160
all addresses before 2014 use 2^160

2015 addresses use ?
2016 addresses use ?
2017 addresses use ?

2019 addresses use 2^256

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