Bitcoin Wiki

Bitcoin’s Security and Hash Rate Explained

Bitcoin’s Security and Hash Rate Explained
As the Bitcoin hash rate reaches new all-time highs, there’s never been a better time to discuss blockchain security and its relation to the hashing power and the Proof of Work (PoW) that feed the network. The Bitcoin system is based on a form of decentralized trust, heavily relying on cryptography. This makes its blockchain highly secure and able to be used for financial transactions and other operations requiring a trustless ledger.
Far from popular belief, cryptography dates back to thousands of years ago. The same root of the word encryption — crypt — comes from the Greek word ‘kryptos’, meaning hidden or secret. Indeed, humans have always wanted to keep some information private. The Assyrians, the Chinese, the Romans, and the Greeks, they all tried over the centuries to conceal some information like trade deals or manufacturing secrets by using symbols or ciphers carved in stone or leather. In 1900 BC, Egyptians used hieroglyphics and experts often refer to them as the first example of cryptography.
Back to our days, Bitcoin uses cryptographic technologies such as:
  1. Cryptographic hash functions (i.e. SHA-256 and RIPEMD-160)
  2. Public Key Cryptography (i.e. ECDSA — the Elliptic Curve Digital Signature Algorithm)
While Public Key Cryptography, bitcoin addresses, and digital signatures are used to provide ownership of bitcoins, the SHA-256 hash function is used to verify data and block integrity and to establish the chronological order of the blockchain. A cryptographic hash function is a mathematical function that verifies the integrity of data by transforming it into a unique unidentifiable code.
Here is a graphic example to make things more clear:

– Extract from the MOOC (Massive Open Online Course) in Digital Currencies at the University of Nicosia.
Furthermore, hash functions are used as part of the PoW algorithm, which is a prominent part of the Bitcoin mining algorithm and this is what is of more interest to understand the security of the network. Mining creates new bitcoins in each block, almost like a central bank printing new money and creates trust by ensuring that transactions are confirmed only when enough computational power is devoted to the block that contains them. More blocks mean more computation, which means more trust.
With PoW, miners compete against each other to complete transactions on the network and get rewarded. Basically they need to solve a complicated mathematical puzzle and a possibility to easily prove the solution. The more hashing power, the higher the chance to resolve the puzzle and therefore perform the proof of work. In more simple words, bitcoins exist thanks to a peer to peer network that helps validate transactions in the ledger and provides enough trust to avoid that a third party is involved in the process. It also exists because miners give it life by resolving that computational puzzle, through the mining reward incentive they are receiving.
For more info, contact directly or email at [email protected].
Tel +357 70007828
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submitted by BlockDotCo to u/BlockDotCo [link] [comments]

Is Crypto Currency truly at risk due to Quantum Computers, and what can you do about it?

Is Crypto Currency truly at risk due to Quantum Computers, and what can you do about it?

There is no denying that the Quantum revolution is coming. Security protocols for the internet, banking, telecommunications, etc... are all at risk, and your Bitcoins (and alt-cryptos) are next!
This article is not really about quantum computers[i], but, rather, how they will affect the future of cryptocurrency, and what steps a smart investor will take. Since this is a complicated subject, my intention is to provide just enough relevant information without being too “techy.”

The Quantum Evolution

In 1982, Nobel winning physicist, Richard Feynman, hypothesized how quantum computers[ii] would be used in modern life.
Just one year later, Apple released the “Apple Lisa”[iii] – a home computer with a 7.89MHz processor and a whopping 5MB hard drive, and, if you enjoy nostalgia, it used 5.25in floppy disks.
Today, we walk around with portable devices that are thousands of times more powerful, and, yet, our modern day computers still work in a simple manner, with simple math, and simple operators[iv]. They now just do it so fast and efficient that we forget what’s happening behind the scenes.
No doubt, the human race is accelerating at a remarkable speed, and we’ve become obsessed with quantifying everything - from the everyday details of life to the entire universe[v]. Not only do we know how to precisely measure elementary particles, we also know how to control their actions!
Yet, even with all this advancement, modern computers cannot “crack” cryptocurrencies without the use of a great deal more computing power, and since it’s more than the planet can currently supply, it could take millions, if not billions, of years.
However, what current computers can’t do, quantum computers can!
So, how can something that was conceptualized in the 1980’s, and, as of yet, has no practical application, compromise cryptocurrencies and take over Bitcoin?
To best answer this question, let’s begin by looking at a bitcoin address.

What exactly is a Bitcoin address?

Well, in layman terms, a Bitcoin address is used to send and receive Bitcoins, and looking a bit closer (excuse the pun), it has two parts:[vi]
A public key that is openly shared with the world to accept payments. A public key that is derived from the private key. The private key is made up of 256 bits of information in a (hopefully) random order. This 256 bit code is 64 characters long (in the range of 0-9/a-f) and further compressed into a 52 character code (using RIPEMD-160).
NOTE: Although many people talk about Bitcoin encryption, Bitcoin does not use Encryption. Instead, Bitcoin uses a hashing algorithm (for more info, please see endnote below[vii]).
Now, back to understanding the private key:
The Bitcoin address “1EHNa6Q4Jz2uvNExL497mE43ikXhwF6kZm” translates to a private key of “5HpHagT65TZzG1PH3CSu63k8DbpvD8s5ip4nEB3kEsreAnchuDf” which further translates to a 256 bit private key of “0000000000000000000000000000000000000000000000000000000000000001” (this should go without saying, but do not use this address/private key because it was compromised long ago.) Although there are a few more calculations that go behind the scenes, these are the most relevant details.
Now, to access a Bitcoin address, you first need the private key, and from this private key, the public key is derived. With current computers, it’s classically impractical to attempt to find a private key based on a public key. Simply put, you need the private key to know the public key.
However, it has already been theorized (and technically proven) that due to private key compression, multiple private keys can be used to access the same public key (aka address). This means that your Bitcoin address has multiple private keys associated with it, and, if someone accidentally discovers or “cracks” any one of those private keys, they have access to all the funds in that specific address.
There is even a pool of a few dedicated people hunting for these potential overlaps[viii], and they are, in fact, getting very efficient at it. The creator of the pool also has a website listing every possible Bitcoin private key/address in existence[ix], and, as of this writing, the pool averages 204 trillion keys per day!
But wait! Before you get scared and start panic selling, the probability of finding a Bitcoin address containing funds (or even being used) is highly unlikely – nevertheless, still possible!
However, the more Bitcoin users, the more likely a “collision” (finding overlapping private/public key pairs)! You see, the security of a Bitcoin address is simply based on large numbers! How large? Well, according to my math, 1.157920892373x1077 potential private keys exist (that number represents over 9,500 digits in length! For some perspective, this entire article contains just over 14,000 characters. Therefore, the total number of Bitcoin addresses is so great that the probability of finding an active address with funds is infinitesimal.

So, how do Quantum Computers present a threat?

At this point, you might be thinking, “How can a quantum computer defeat this overwhelming number of possibilities?” Well, to put it simple; Superposition and Entanglement[x].
Superposition allows a quantum bit (qbit) to be in multiple states at the same time. Entanglement allows an observer to know the measurement of a particle in any location in the universe. If you have ever heard Einstein’s quote, “Spooky Action at a Distance,” he was talking about Entanglement!
To give you an idea of how this works, imagine how efficient you would be if you could make your coffee, drive your car, and walk your dog all at the same time, while also knowing the temperature of your coffee before drinking, the current maintenance requirements for your car, and even what your dog is thinking! In a nutshell, quantum computers have the ability to process and analyze countless bits of information simultaneously – and so fast, and in such a different way, that no human mind can comprehend!
At this stage, it is estimated that the Bitcoin address hash algorithm will be defeated by quantum computers before 2028 (and quite possibly much sooner)! The NSA has even stated that the SHA256 hash algorithm (the same hash algorithm that Bitcoin uses) is no longer considered secure, and, as a result, the NSA has now moved to new hashing techniques, and that was in 2016! Prior to that, in 2014, the NSA also invested a large amount of money in a research program called “Penetrating Hard Targets project”[xi] which was used for further Quantum Computer study and how to break “strong encryption and hashing algorithms.” Does NSA know something they’re not saying or are they just preemptively preparing?
Nonetheless, before long, we will be in a post-quantum cryptography world where quantum computers can crack crypto addresses and take all the funds in any wallet.

What are Bitcoin core developers doing about this threat?

Well, as of now, absolutely nothing. Quantum computers are not considered a threat by Bitcoin developers nor by most of the crypto-community. I’m sure when the time comes, Bitcoin core developers will implement a new cryptographic algorithm that all future addresses/transactions will utilize. However, will this happen before post-quantum cryptography[xii]?
Moreover, even after new cryptographic implementation, what about all the old addresses? Well, if your address has been actively used on the network (sending funds), it will be in imminent danger of a quantum attack. Therefore, everyone who is holding funds in an old address will need to send their funds to a new address (using a quantum safe crypto-format). If you think network congestion is a problem now, just wait…
Additionally, there is the potential that the transition to a new hashing algorithm will require a hard fork (a soft fork may also suffice), and this could result in a serious problem because there should not be multiple copies of the same blockchain/ledger. If one fork gets attacked, the address on the other fork is also compromised. As a side-note, the blockchain Nebulas[xiii] will have the ability to modify the base blockchain software without any forks. This includes adding new and more secure hashing algorithms over time! Nebulas is due to be released in 2018.

Who would want to attack Bitcoin?

Bitcoin and cryptocurrency represent a threat to the controlling financial system of our modern economy. Entire countries have outright banned cryptocurrency[xiv] and even arrested people[xv], and while discrediting it, some countries are copying cryptocurrency to use (and control) in their economy[xvi]!
Furthermore, Visa[xvii], Mastercard[xviii], Discover[xix], and most banks act like they want nothing to do with cryptocurrency, all the while seeing the potential of blockchain technology and developing their own[xx]. Just like any disruptive technology, Bitcoin and cryptocurrencies have their fair share of enemies!
As of now, quantum computers are being developed by some of the largest companies in the world, as well as private government agencies.
No doubt, we will see a post-quantum cryptography world sooner than most realize. By that point, who knows how long “3 letter agencies” will have been using quantum technology - and what they’ll be capable of!

What can we do to protect ourselves today?

Of course, the best option is to start looking at how Bitcoin can implement new cryptographic features immediately, but it will take time, and we have seen how slow the process can be just for scaling[xxi].
The other thing we can do is use a Bitcoin address only once for outgoing transactions. When quantum computers attack Bitcoin (and other crypto currencies), their first target will be addresses that have outgoing transactions on the blockchain that contain funds.
This is due to the fact that when computers first attempt to crack a Bitcoin address, the starting point is when a transaction becomes public. In other words, when the transaction is first signed – a signed transaction is a digital signature derived from the private key, and it validates the transaction on the network. Compared to classical computers, quantum computers can exponentially extrapolate this information.
Initially, Bitcoin Core Software might provide some level of protection because it only uses an address once, and then sends the remaining balance (if any) to another address in your keypool. However, third party Bitcoin wallets can and do use an address multiple times for outgoing transactions. For instance, this could be a big problem for users that accept donations (if they don’t update their donation address every time they remove funds). The biggest downside to Bitcoin Core Software is the amount of hard-drive space required, as well as diligently retaining an up-to-date copy of the entire blockchain ledger.
Nonetheless, as quantum computers evolve, they will inevitably render SHA256 vulnerable, and although this will be one of the first hash algorithms cracked by quantum computers, it won’t be the last!

Are any cryptocurrencies planning for the post-quantum cryptography world?

Yes, indeed, there are! Here is a short list of ones you may want to know more about:

Full disclosure:

Although I am in no way associated with any project listed above, I do hold coins in all as well as Bitcoin, Litecoin and many others.
The thoughts above are based on my personal research, but I make no claims to being a quantum scientist or cryptographer. So, don’t take my word for anything. Instead, do your own research and draw your own conclusions. I’ve included many references below, but there are many more to explore.
In conclusion, the intention of this article is not to create fear or panic, nor any other negative effects. It is simply to educate. If you see an error in any of my statements, please, politely, let me know, and I will do my best to update the error.
Thanks for reading!


[i] – A great video explaining quantum computers.
[ii] - A brief history of quantum computing.
[iii] - More than you would ever want to know about the Apple Lisa.
[iv] - Want to learn more about computer science? Here is a great crash course for it!
[v] - What does quantify mean?
[vi] - More info about Bitcoin private keys.
[vii] - A good example of the deference between Hash and Encryption
[viii] - The Large Bitcoin Collider.
[ix] - A list of every possible Bitcoin private key. This website is a clever way of converting the 64 character uncompressed key to the private key 128 at a time. Since it is impossible to save all this data in a database and search, it is not considered a threat! It’s equated with looking for a single needle on the entire planet.
[x] – Brief overview of Superposition and Entanglement.
[xi] – A review of the Penetrating Hard Targets project.
[xii] - Explains post-quantum cryptography.
[xiii] - The nebulas project has some amazing technology planned in their roadmap. They are currently in testnet stage with initial launch expected taking place in a few weeks. If you don’t know about Nebulas, you should check them out. [xiv] - Country’s stance on crypto currencies.
[xv] - Don’t be a miner in Venezuela!
[xvi] - Russia’s plan for their own crypto currency.
[xvii] - Recent attack from visa against crypto currency.
[xviii] - Mastercards position about Bitcoin.
[xix] - Discovers position about Bitcoin.
[xx] - Mastercard is making their own blockchain.
[xxi] - News about Bitcoin capacity. Not a lot of news…
[xxii] - IOTA and quantum encryption.
[xxiii] - The whitepaper of Winternitz One-Time Signature Scheme
[xxiv] - The Cardano project roadmap.
[xxv] - More about the BLISS hash system.
[xxvi] - Home of the Ethereum project.
[xxvii] – SHA3 hash algorithm vs quantum computers.
[xxviii] - Lamport signature information.
[xxix] - Home of the Quantum Resistant Ledger project.
submitted by satoshibytes to CryptoCurrency [link] [comments]

BIP Number Request: Open Asset | Nicolas Dorier | May 26 2016

Nicolas Dorier on May 26 2016:
Open Asset is a simple and well known colored coin protocol made by Flavien
Charlon, which has been around for more than two years ago.
Open Asset is OP_RETURN to store coin's color. Since then, the only
modification to the protocol has been for allowing OA data to be into any
push into an OP_RETURN.
The protocol is here:
I asked to Flavien Charlon if he was OK if I submit the protocol to the
mailing list before posting.
Additional BIP number might be required to cover for example the "colored
address" format:
But I will do it in a separate request.
Here is the core of the Open Asset specification:
Title: Open Assets Protocol (OAP/1.0)
Author: Flavien Charlon
Created: 2013-12-12
This document describes a protocol used for storing and transferring
custom, non-native assets on the Blockchain. Assets are represented by
tokens called colored coins.
An issuer would first issue colored coins and associate them with a
formal or informal promise that he will redeem the coins according to
terms he has defined. Colored coins can then be transferred using
transactions that preserve the quantity of every asset.
In the current Bitcoin implementation, outputs represent a quantity of
Bitcoin, secured by an output script. With the Open Assets Protocol,
outputs can encapsulate a quantity of a user-defined asset on top of
that Bitcoin amount.
There are many applications:
could then be traded frictionlessly through the Bitcoin
could withdraw and deposit money in colored coins, and trade those, or
use them to pay for goods and services. The Blockchain becomes a
system allowing to transact not only in Bitcoin, but in any currency.
of colored coins. The door would only open when presented with a
wallet containing that specific coin.
==Protocol Overview==
Outputs using the Open Assets Protocol to store an asset have two new
asset stored on the output.
many units of that asset are stored on the output.
This document describes how the asset ID and asset quantity of an
output are calculated.
Each output in the Blockchain can be either colored or uncolored:
both undefined).
non-null asset ID.
The ID of an asset is the RIPEMD-160 hash of the SHA-256 hash of the
output script referenced by the first input of the transaction that
initially issued that asset (script_hash =
RIPEMD160(SHA256(script))). An issuer can reissue more of an
already existing asset as long as they retain the private key for that
asset ID. Assets on two different outputs can only be mixed together
if they have the same asset ID.
Like addresses, asset IDs can be represented in base 58. They must use
version byte 23 (115 in TestNet3) when represented in base 58. The
base 58 representation of an asset ID therefore starts with the
character 'A' in MainNet.
The process to generate an asset ID and the matching private key is
described in the following example:

The issuer first generates a private key:


He calculates the corresponding address:


Next, he builds the Pay-to-PubKey-Hash script associated to that

address: OP_DUP OP_HASH160
010966776006953D5567439E5E39F86A0D273BEE OP_EQUALVERIFY

The script is hashed: 36e0ea8e93eaa0285d641305f4c81e563aa570a2

Finally, the hash is converted to a base 58 string with checksum

using version byte 23:
The private key from the first step is required to issue assets
identified by the asset ID
ALn3aK1fSuG27N96UGYB1kUYUpGKRhBuBC. This acts as a
digital signature, and gives the guarantee that nobody else but the
original issuer is able to issue assets identified by this specific
asset ID.
==Open Assets Transactions==
Transactions relevant to the Open Assets Protocol must have a special
output called the marker output. This allows clients to recognize such
transactions. Open Assets transactions can be used to issue new
assets, or transfer ownership of assets.
Transactions that are not recognized as an Open Assets transaction are
considered as having all their outputs uncolored.
===Marker output===
The marker output can have a zero or non-zero value. The marker output
starts with the OP_RETURN opcode, and can be followed by any sequence
of opcodes, but it must contain a PUSHDATA opcode containing a
parsable Open Assets marker payload. If multiple parsable PUSHDATA
opcodes exist in the same output, the first one is used, and the other
ones are ignored.
If multiple valid marker outputs exist in the same transaction, the
first one is used and the other ones are considered as regular
outputs. If no valid marker output exists in the transaction, all
outputs are considered uncolored.
The payload as defined by the Open Assets protocol has the following format:
! Field !! Description !! Size
! OAP Marker || A tag indicating that this transaction is an
Open Assets transaction. It is always 0x4f41. || 2 bytes
! Version number || The major revision number of the Open Assets
Protocol. For this version, it is 1 (0x0100). || 2 bytes
! Asset quantity count || A
var-integer] representing the number of items in the asset
quantity list field. || 1-9 bytes
! Asset quantity list || A list of zero or more
[ LEB128-encoded] unsigned integers
representing the asset quantity of every output in order (excluding
the marker output). || Variable
! Metadata length || The
var-integer] encoded length of the metadata field. || 1-9
! Metadata || Arbitrary metadata to be associated with
this transaction. This can be empty. || Variable
Possible formats for the metadata field are outside of
scope of this protocol, and may be described in separate protocol
specifications building on top of this one.
The asset quantity list field is used to determine the
asset quantity of each output. Each integer is encoded using variable
length [ LEB128] encoding (also
used in [
Google Protocol Buffers]). If the LEB128-encoded asset quantity of any
output exceeds 9 bytes, the marker output is deemed invalid. The
maximum valid asset quantity for an output is 263 - 1
If the marker output is malformed, it is considered non-parsable.
Coinbase transactions and transactions with zero inputs cannot have a
valid marker output, even if it would be otherwise considered valid.
If there are less items in the asset quantity list than
the number of colorable outputs (all the outputs except the marker
output), the outputs in excess receive an asset quantity of zero. If
there are more items in the asset quantity list than the
number of colorable outputs, the marker output is deemed invalid. The
marker output is always uncolored.
After the asset quantity list has been used to assign an
asset quantity to every output, asset IDs are assigned to outputs.
Outputs before the marker output are used for asset issuance, and
outputs after the marker output are used for asset transfer.
This example illustrates how a marker output is decoded. Assuming the
marker output is output 1:
Data in the marker output Description ----------------------------- 
0x6a The OP_RETURN opcode. 0x10 The PUSHDATA opcode for a 16 bytes payload. 0x4f 0x41 The Open Assets Protocol tag. 0x01 0x00 Version 1 of the protocol. 0x03 There are 3 items in the asset quantity list. 0xac 0x02 0x00 0xe5 0x8e 0x26 The asset quantity list: - '0xac 0x02' means output 0 has an 
asset quantity of 300.
 - Output 1 is skipped and has an 
asset quantity of 0
 because it is the marker output. - '0x00' means output 2 has an 
asset quantity of 0.
 - '0xe5 0x8e 0x26' means output 3 
has an asset quantity of 624,485.
 - Outputs after output 3 (if any) 
have an asset quantity of 0.
0x04 The metadata is 4 bytes long. 0x12 0x34 0x56 0x78 Some arbitrary metadata. 
===Asset issuance outputs===
All the outputs before the marker output are used for asset issuance.
All outputs preceding the marker output and with a non-zero asset ...[message truncated here by reddit bot]...
submitted by dev_list_bot to bitcoin_devlist [link] [comments]

[Kali 17.1] JtR support for pkzip dropped?

Hi all, I'm just trying my hand on the okcupid challenge (view source of It includes four encrypted zip files. I wanted to try the easy way first and use john, but it seems on Kali 17.1 JtR does not support the pkzip format anymore?
[email protected]:~# john --list=formats 
descrypt, bsdicrypt, md5crypt, bcrypt, scrypt, LM, AFS, tripcode, dummy, dynamic_n, bfegg, dmd5, dominosec, dominosec8, EPI, Fortigate, FormSpring, has-160, hdaa, ipb2, krb4, krb5, KeePass, MSCHAPv2, mschapv2-naive, mysql, nethalflm, netlm, netlmv2, netntlm, netntlm-naive, netntlmv2, md5ns, NT, osc, PHPS, po, skey, SybaseASE, xsha, xsha512, agilekeychain, aix-ssha1, aix-ssha256, aix-ssha512, asa-md5, Bitcoin, Blackberry-ES10, WoWSRP, Blockchain, chap, Clipperz, cloudkeychain, cq, CRC32, sha1crypt, sha256crypt, sha512crypt, Citrix_NS10, dahua, Django, django-scrypt, dmg, dragonfly3-32, dragonfly3-64, dragonfly4-32, dragonfly4-64, Drupal7, eCryptfs, EFS, eigrp, EncFS, EPiServer, fde, gost, gpg, HAVAL-128-4, HAVAL-256-3, HMAC-MD5, HMAC-SHA1, HMAC-SHA224, HMAC-SHA256, HMAC-SHA384, HMAC-SHA512, hMailServer, hsrp, IKE, keychain, keyring, keystore, known_hosts, krb5-18, krb5pa-sha1, kwallet, lp, lotus5, lotus85, LUKS, MD2, md4-gen, mdc2, MediaWiki, MongoDB, Mozilla, mscash, mscash2, krb5pa-md5, mssql, mssql05, mssql12, mysql-sha1, mysqlna, net-md5, net-sha1, nk, nsldap, o5logon, ODF, Office, oldoffice, OpenBSD-SoftRAID, openssl-enc, oracle, oracle11, Oracle12C, Panama, pbkdf2-hmac-md5, PBKDF2-HMAC-SHA1, PBKDF2-HMAC-SHA256, PBKDF2-HMAC-SHA512, PDF, PFX, phpass, pix-md5, plaintext, pomelo, postgres, PST, PuTTY, pwsafe, RACF, RAdmin, RAKP, rar, RAR5, Raw-SHA512, Raw-Blake2, Raw-Keccak, Raw-Keccak-256, Raw-MD4, Raw-MD5, Raw-SHA1, Raw-SHA1-Linkedin, Raw-SHA224, Raw-SHA256, Raw-SHA256-ng, Raw-SHA3, Raw-SHA384, Raw-SHA512-ng, Raw-SHA, Raw-MD5u, ripemd-128, ripemd-160, rsvp, Siemens-S7, Salted-SHA1, SSHA512, sapb, sapg, saph, 7z, sha1-gen, Raw-SHA1-ng, SIP, skein-256, skein-512, aix-smd5, Snefru-128, Snefru-256, LastPass, SSH, SSH-ng, Stribog-256, Stribog-512, STRIP, SunMD5, sxc, Sybase-PROP, tcp-md5, Tiger, tc_aes_xts, tc_ripemd160, tc_sha512, tc_whirlpool, VNC, vtp, wbb3, whirlpool, whirlpool0, whirlpool1, wpapsk, ZIP, NT-old, crypt
Am I missing something? Thanks!
submitted by mrquisda to AskNetsec [link] [comments]

How to steal coins if some one-way function is flawed?

Dear Bitcoin
I'm trying to grasp the different implications if any one-way function of the address creation process is flawed. I've come up with two different types of potential flaws
Both of these imaginary flaws can be found in either the specification or in an implementation. I only focus on specification flaws here, but I do think the same analysis holds for implementation flaws as well.
The tables list my understanding of what needs to be done in order to steal someone's coins, given that only the public key hash or script hash is known.
Are these tables correct? Is there any important information to add?
Version 0 addresses
Function Small output space Can craft input
Random number generator Doomed! N/A
Public key derivation Doomed! Must pre-image attack RIPEMD(SHA())
SHA256 Doomed! Must pre-image attack RIPEMD AND brute force public key derivation
RIPEMD160 Doomed! Must brute force SHA(pubkeyderivation())
Pay-to-script-hash addresses
Function Small output space Can craft input
SHA256 Doomed! If I know the script [1], I can craft a second script with same SHA256 value. If script is not known, I need to pre-image attack RIPEMD160
RIPEMD160 Doomed! Must pre-image attack SHA256
[1] is very likely. For example a party in a multisig address knows the script and can rip off the other parties.
We are doomed if any of the functions are brute-forceable. That means that the more fancy one-way functions we use, the more vulnerable we are.
submitted by kallerosenbaum to Bitcoin [link] [comments]

Creating bitcoin addresses (tech questions)

I'm currently looking into the fundamentals of creating new bitcoin addresses and private keys. I have made a php-script that converts any 64-byte hex-key into both a private key and a bitcoin address. When i was researching the specifications i found this example on "" "hello 2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824 (first round is sha-256) b6a9c8c230722b7c748331a8b450f05566dc7d0f (with ripemd-160)" The ripemd-160 address contains 1 satoshi which can be seen on blockchain. Is there any way to find the private key to this address or is that impossible since since just "sha + ripemd" isnt the protocol and the result is just a random address with unknown private key? Secondly i'm also generating vanity addresses with oclvanitygen. I tried generating a few addresses with 7 letters (ignoring case) like "1satoshi" and "1qwertyu". But it seems that they have different difficulity (estimated time to 50%) even though they have the same amount of letters. I can't seem to find an explanation to that.
submitted by bitcoinqwerty to Bitcoin [link] [comments]

Role of the checksum

In my free time I am trying to learn and understand Bitcoin as much as possible.
The generation of the private/public key pair is made through the sec256k1 parameters of the ECDSA elliptical curve. The resulting public key is then sent through a series of hashing (RIP-EMD, SHA-256) as seen here to generate the eventual public Bitcoin address. During the hashing functions, the first 4 bytes of the second SHA-256 hash are taken and added onto the RIPEMD-160 hash and these 4 bytes are what is known as the checksum.
My question is what exactly is the role of the checksum? Based on this page it looks like the checksum is essentially used to verify that the Bitcoin address is indeed associated with a particular private key. Are wallet clients using the checksum to make this verification? Can anyone explain how this works?
submitted by bopplegurp to BitcoinBeginners [link] [comments]

Idea for safely implementing "Opt-In Full-RBF": Make it receiver opt-in rather than sender opt-in.

There are currently a lot of arguments against opt-in RBF about how it could become a usability nightmare and can enable double spends against unwitting people. This stems from the fact that it's opt-in by the sender and this requires a certain amount of knowledge by the receiver to avoid being scammed. But what if it was opt-in by the receiver instead? Then the sender has no way of issuing a RBF transaction against someone who is unwilling to accept a RBF transaction.
Currently there is no way to do this. The Bitcoin network is unaware of anything to do with the receiver of a transaction other than the public key hash or script hash. It can however tell the difference between the two types of keys. Standard public key hashes are prefixed with "1" and script hash keys are prefixed with "3".
I'm suggesting a hard fork that adds 2 new prefixes to public addresses. The new prefixes could be anything, but for the sake of this example let's say the the new prefixes are "R" and "r". "R" would become the prefix for public key hash addresses that are willing to accept RBF transactions and "r" for opt-in RBF script hash addresses. Now there is no need for transactions to be declared by the sender as RBF. Nodes and miners will simply reject any double spend attempts unless all outputs of the transaction are prefixed with either "R" or "r". The sender could even choose to opt-out of RBF by using a non-RBF prefixed address as one of the change outputs.
This does create an issue where you can spoof the intent of the receiver by changing the prefix on the address, so the function used to calculate the public address would need to be slightly different. The sender can't be allowed to reverse engineer an "R" address from a "1" address. There are two possible solutions here.
Option 1: Make a small change to the public key hashing algorithm. This could be something as simple as performing the RIPEMD-160 hash twice instead of once when creating a RBF address. This method has the benefit of not adding any cryptographic complexity to the system but the cons are that once you spend from an address and reveal the true public key, anyone can generate both public addresses. You only have the security of receiving non-RBF transactions exclusively as long as you don't reuse the address once you spend from it, or if you generate a new address for each incoming transaction. Also, wallet and block explorer software would need to be updated so that the possibility of two different addresses pointing to the same public key won't break it.
Option 2: Use a different ECDSA curve. This is the cleanest option when it comes to usability and writing code, but at the expense of adding more cryptographic complexity to the system. More points of failure to worry about.
Personally I think option 1 might be better. Address reuse is already discouraged and thanks to the popularity of HD wallets, following that rule is not that big a deal.
submitted by testing1567 to btc [link] [comments]

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From Bitcoin Wiki. Jump to: navigation, search. RIPEMD-160 is a cryptographic hash function based upon the Merkle–Damgård construction. It is used in the Bitcoin standard. It is a a strengthened version of the RIPEMD algorithm which produces a 128 bit hash digest while the RIPEMD-160 algorithm produces a 160-bit output. The compression function is made up of 80 stages made up of 5 blocks ... The input is hashed using RIPEMD-160. OP_SHA1 167 0xa7 in hash The input is hashed using SHA-1. OP_SHA256 168 0xa8 in hash The input is hashed using SHA-256. OP_HASH160 169 0xa9 in hash The input is hashed twice: first with SHA-256 and then with RIPEMD-160. OP_HASH256 170 0xaa in hash The input is hashed two times with SHA-256. OP_CODESEPARATOR 171 RIPEMD-160 (RACE Integrity Primitives Evaluation Message Digest) is a cryptographic hash function based upon the Merkle–Damgård construction.. RIPEMD-160 is an improved, 160-bit version of the original RIPEMD, and the most common version in the family. RIPEMD-160 was designed in the open academic community, in contrast to the NSA-designed SHA-1 and SHA-2 algorithms. Bitcoin is a decentralized digital currency that enables instant payments to anyone, anywhere in the world. Bitcoin uses peer-to-peer technology to operate with no central authority: transaction management and money issuance are carried out collectively by the network. The original Bitcoin software by Satoshi Nakamoto was released under the MIT license. . Most client software, derived or "from ... RIPEMD-160 is a cryptographic hash function based upon the Merkle–Damgård construction. It is used in the Bitcoin standard. It is a a strengthened version of the RIPEMD algorithm which produces a 128 bit hash digest while the RIPEMD-160 algorithm produces a 160-bit output. The compression function is made up of 80 stages made up of 5 blocks that run 16 times each. This pattern runs twice ...

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How to hack bitcoin addresses! This is a new working program 2020 for selecting private keys BTC!

The program does not require an Internet connection, since the generation of bitcoin addresses with private keys occurs, SHA 256, RIPEMD-160 , base58 are already built into the program Loading... The program does not require an Internet connection, since the generation of bitcoin addresses with private keys occurs, SHA 256, RIPEMD-160 , base58 are already built into the program Loading... Cuando Satoshi Nakamoto publicó su whitepaper de Bitcoin, explicó el porque y como uso de SHA-256 y RIPEMD-160 en Bitcoin. Desde entonces, la tecnología blockchain ha evolucionado mucho, pero ... The program does not require an Internet connection, since the generation of bitcoin addresses with private keys occurs, SHA 256, RIPEMD-160 , base58 are already built into the program Loading... Bitcoin currently uses the following cryptographic algorithms: ECDSA, SHA-256 and RIPEMD-160. A quantum computer can crack only the elliptical ECDSA curve algorithm, which can be replaced with a ...