SHA256 - Can it be compromised? : Bitcoin

I made my own Blockchain in Java (Part 2) now with Source Code!

Hello all! Same guy that posted about a Java Bitcoin Address Generator. I've completed my blockchain mockup and I couldn't be happier with it. Although it doesn't have persistent state and doesn't use new addresses as Change addresses (since the wallets are not HD, just single-keypair wallets), I learned a lot from doing this.
It really does help to understand the complexity of cryptocurrencies when you try to make it from scratch by yourself. There's a ton of security behind bitcoin, and some of it may seem absurd (SHA-256 hashing into RIPEMD-160 into 2x SHA-256 like Damn... all for a checksum).
If you want to mess around with the program, I've uploaded it to Github (Link here). It's a functioning wallet-type program that has Accounts you can switch between where each account has its own KeyPair that you can then send and receive funds to. There is a block reward for mining new blocks that is distributed from the "coinbase" wallet.
NOTE: This is intended to be for educational purposes and should in no way be considered a real cryptocurrency/blockchain. It only runs for the time you have it open and loses all information when closed. The addresses it generates ARE valid bitcoin addresses that you can use, but do so at your own risk and know what you're doing. There is no seed for the addresses that are generated.
submitted by Septem_151 to Bitcoin [link] [comments]

We need a standard for Bitcoin blockchain timestamps! Proposal Inside! Feedback please!

Dear Bitcoiners and Bitcoinerettes
I have recently found great interest in using the Bitcoin blockchain for secure and trustless timestamping. This interest was mainly raised as I would have loved to have proof of certain data I and others produced in the past. I am not in the situation to need the proof now, but It could have come in handy one day. I previously asked on reddit about advice regarding creation of an email plugin which would keep timestamps for all my emails. I imagined this plugin to timestamp based on certain filter criteria.
The reactions on reddit were quite negative: Too expensive, too much bloat, blockchain spam. At the time I was discouraged and let it slip away as it seemed unfeasible.
I started to study the current implementations and services and created this overview:
Bitcoin Blockchain Timestamping Overview
I have no affiliation with any of these and I have also not tried all of these services!
After studying these concepts which I found, I came to several conclusions:
I think we are in need of a standard which will be used more often. Only if we have a standard which lots of users follow, Bitcoin timestamps can be widely used and accepted. Just imagine a court case where someone claims to have such a timestamp. Technical experts will have to be called in to state that this is in fact as close to proof as it gets that the timestamp was in fact made prior to date X. Now if everyone does it differently, everyone will have to pay for their own experts and it will take much longer until these timestamps are accepted plus it will overall be more expensive to get them accepted, if there are several predominant types. If we follow a standard these timestamps could get a certain credibility amongst non-technical people and would be accepted much faster.
So what would be ideal requirements for such a standard?
From these requirements I figured the following concept would be best:
To verify A timestamp one needs the following:
Actually it was sipa who pointed me to ChronoBit (in the list linked above) and making use of of Merkle trees to reduce bloat. My proposal as pointed out above derives from the concept of CronoBit in that it still creates a transaction. However, it borrows the concept of the hash tree from CronoBit and I guess from Bitcoin itself too ;-)
While ChronoBit is fully p2p and decentralized it bears the problem that you either need to be mining on p2p-pool yourself, or rely on others to be mining for you. The timestamps are somewhat limited to blocks found by p2p-pool. It is elegant as you have a direct connection to the block hash and no additional transactions are needed.
I am look at using a one Satoshi transaction for x timestamps is like forging a little unspendable colored coin which serves as anchor point for many timestamp participants.
A single stamper (private or service) can literally create thousands of timestamps in a daily transaction. The client must store a little bit more data compared to single timestamp models. That is not an awful lot of data even for thousands of documents; e.g. 1500 digits proof per document (including some identifiers) would suffice to join forces and have 250’000 timestamps in one transaction.
I guess the standard needs to be as flexible as possible. The format must be similar to PGP signatures or so. Something like: {document’s hash; transaction hash, Merkle tree branch depth, Merkle tree branch hashes, claimed blocktime of verified block}
I like the concept because it would enable a fully dynamic level of self crated Merkle tree and service created Merkle tree. Can either be done on top of own full Bitcoin node, or with a service. If a service is used the hash tree can still be continued. The service can do nothing but fool you for some minutes. There are no privacy issues as only hashes are sent in the first place. After the service created and sent the proof, it can vanish without the timestamp being lost for the user; 3rd party trust will not be a critical thing for most users.
I also want to discuss the way the address is created in my proposal above. Some current implementations create a private key first and then derive the address from it. This makes the transacted Satoshi potentially prunable. Someone could spend it with the private key which is commonly known. I want that Satoshi stuck forever.
With this scheme I think it would be feasible to timestamp as many emails and documents as I want without having huge costs and the bloat is somewhat justifiable...
After your valued feedback I would like to try to put together a paper and some kind of demo implementation.
Best regards and thanks for reading.
SimonBelmond
Things which are not entirely clear to me:
submitted by SimonBelmond to Bitcoin [link] [comments]

What is a Bitcoin hash and SHA-256 - YouTube 20ft Bitcoin mining container for Canaan Avalon SHA256 ASICs by Power Mining what is SHA-256 Algorithm  mining Algorithm What is SHA256?  Bitcoin mining using Raspberry Pi What is a Bitcoin hash and SHA-256 - YouTube

It's basically just a "checksum", and it is NOT reversible. A SHA256 hash is only 32 characters long. If you CAN reverse that, I can just give you the 32 character hash of a 4 GB DVD ISO in a single chat message, and you can REVERSE-ENGINEER the ENTIRE 4GB ISO from those 32 characters. Of course, this isn't possible. FYI, almost ALL current security systems (e.g. the HTTPS used on your online ... SHA-256 is a member of the SHA-2 cryptographic hash functions designed by the NSA. SHA stands for Secure Hash Algorithm. Cryptographic hash functions are mathematical operations run on digital data; by comparing the computed "hash" (the output from execution of the algorithm) to a known and expected hash value, a person can determine the data's integrity. Mining; Creation of Bitcoin addressess; Mining. Mining is a process by which new coins are introduced into the existing circulating supply of the Bitcoin protocol, as well as a method used to secure the Bitcoin network. For an individual to be eligible to add a block to the Bitcoin blockchain, they must first operate what is known as a mining node. Upon successfully setting up a mining node ... SHA256 algorithm generates an almost-unique, fixed size 256-bit (32-byte) hash. Hash is so called a one way function. This makes it suitable for checking integrity of your data, challenge hash authentication, anti-tamper, digital signatures, blockchain. With the newest hardware (CPU and GPU) improvements it is become possible to decrypt SHA256 algorithm back. So it is no longer recommended to ... Request PDF Optimizing SHA256 in Bitcoin Mining Bitcoin is a "crypto currency", a decentralized electronic payment scheme based on cryptography. It implements a particular type of peer-to-peer ...

[index] [4365] [20807] [36824] [41913] [24191] [37073] [27574] [32697] [3564] [20461]

What is a Bitcoin hash and SHA-256 - YouTube

This video explains the concept of hashing and SHA-256 for newbies. For more information visit http://99bitcoins.com/what-is-bitcoin-hash/ AntMiner S9 + 1600W PSU 11.85Th/s two fan,11850Gh/s Asic Miner, Bitcon Miner, 16nm BTC Mining, Power Consumption 1172w, SHA256 Заказываем здесь: http ... Mining Bitcoin with Excel - Duration: 7:17. Knowledge 181,876 views. 7:17. Pawn Stars: 20 SUPER RARE HIGH VALUE ITEMS ... What is a Bitcoin hash and SHA-256 - Duration: 1:54. Ofir Beigel 64,406 ... This video explains the concept of hashing and SHA-256 for newbies. For the complete text guide visit: http://bit.ly/2DmxbJj Join our 7-day Bitcoin crash cou... The SHA-256 algorithm is used to mine bitcoin, It is worth noting SHA-256 is part of the SHA-2 cryptographic hash(SHA-2 (Secure Hash Algorithm 2) is a set of cryptographic hash functions designed ...

#