Blockchain tutorial 6: Digital signature
Вставка
- Опубліковано 29 бер 2017
- This is part 6 of the Blockchain tutorial explaining what a digital signature is.
In this video series different topics will be explained which will help you to understand blockchain.
Bitcoin released as open source software in 2009 is a cryptocurrency invented by Satoshi Nakamoto (unidentified person or group of persons).
After the introduction of Bitcoin many Bitcoin alternatives were created. These alternate cryptocurrencies are called Altcoins (Litecoin, Dodgecoin etc).
Bitcoin's underlying technology is called Blockchain.
The Blockchain is a distributed decentralized incorruptible database (ledger) that records blocks of digital information. Each block contains a timestamp and a link to a previous block.
Soon people realises that there many other use cases where the Blockchain technology can be applied and not just as a cryptocurrency application.
New Blockchain platforms were created based on the Blockchain technology, one of which is called Ethereum.
Ethereum focuses on running programming code, called smart contracts, on any decentralized application.
Using the new Blockchain platforms, Blockchain technology can be used in supply chain management, healthcare, real estate, identity management, voting, internet of things, etcetera, just to name a few.
Today there is a growing interest in Blockchain not only in the financial sector but also in other sectors.
Explaining how Blockchain works is not easy and for many the Blockchain technology remains an elusive concept.
This video series tries to explain Blockchain to a large audience but from the bottom up.
Keywords often used in Blockchain conversation will be explained.
Each Blockchain video is short and to the point.
It is recommended to watch each video sequentially as I may refer to certain Blockchain topics explained earlier.
Check out all my other Blockchain tutorial videos
goo.gl/aMTFHU
Subscribe to my UA-cam channel
goo.gl/61NFzK
The presentation used in this video tutorial can be found at:
www.mobilefish.com/developer/b...
#mobilefish #blockchain #bitcoin #cryptocurrency #ethereum - Навчання та стиль
The way you explain this term is awesome
Excellent video. At last somebody who goes beyond saying "the sender signs the transaction with his/her private key to generate a digital signature that allows the receiver to verify identity and message", and actually show how this is done!!!!
Thank you! Brilliant! Bravo! This really helped!
Hi, this tutorial on digital signature is getting into the complex part of block chain. Tutorial 6 needs to be view several times for a proper understanding. Not easy, but it's intriguing. Thanks for the tutorial.
Thanks for clearing explaining the confusing topic.
Great explanation!
very nice ... thanks for the demo and very clear.
hi mobilefish , you really a greate explainer, i tried many videos and artical but you are awesome
Thank you! I was looking for this kind of technical explanation!
U are amaizng mannn... U are Making crypto easier by your lectures thanks alot man. High respect for u 🌹
always grateful~~
best explanation
thank you very much.
Thank you!
Thanks!!
This series is youtube gold
have watched this multiple times,but couldn't understand one part - Alice first hashes the data then uses pvt key to encrypt the hash but why hash the data in the first place when you can simply encrypt the data?
Is there will be a validation for this document by other nodes!?
In 2:24, he says the data which is the document is now hashed which gives hash value for comparison. My question is how Bob has the actual data? wasn't he supposed to be the receiver? According to the explanation, so-far he has only decrypted the digital signature which gave him the original hash value which is not the actual data. Can someone please explain.
Thank you!
bob has the actual data. bob is only trying to verify that the sender of data is alice and the data is not changed in any way. So bob rehashes the actual data and decrypts the digital signature using alice's public key to get the hash that will be compared
@@salarhussain6189 which actually means Alice will send 3 pieces of information to Bob : the document unencrypted, her digital signature AND the public key (to decrypt the digital signature to get hash A and to hash the text to get hash B). Right?
Bob receives two separate things: 1) the document and 2) the digital signature, separately. Remember, the digital signature is encrypted with both the document and private key together.He puts the 1) document through the hash and creates that hash value. And then he decrypts the 2) signature with her public key), which reveals another hash value for the document. Then he compares both of those values to make sure that they are exactly the same.
What are the requirements for implementation
Thank you for the video. Would you mind also explain to use the Web3.eth.sign in this case? Much appreciated.
I have created some Web3 API examples: www.mobilefish.com/download/ethereum/web3api.html several months ago (I am not sure if the example still works, as web3 API evolve very fast).
But to be honest I have not use Web3.eth.sign in a real use case..
Many Thanks. Yes, Indeed. The version 1.0 is releasing soon.
Different different algorithms (MD5 and sha1) give same hash function ? While checking (encryption and decryption) digital signature.? Is it possible if encryption with MD5 and decryption with sha1 algorithms ?
Thanks for your tutorial.
1) MD5 and SHA1 are different hash functions and do not produce the same output.
MD5 output size 128 bits
SHA1 output size 160 bits
2) MD5 and SHA1 are hash functions, which means for example a document can be hashed to produce a unique "fingerprint". Which means you cannot create the document with this "fingerprint". Hash functions are one-way functions. MD5 and SHA1 are NOT symmetric or asymmetric key algorithms.
i am working on web3 and try to use web3.eth.call() but struggling to find a right way to apply this one
Sorry, but I have never used that api call before. I did not find a use for it...
Thank you. is it possible we can have the slides?
All slides can be found at:
www.mobilefish.com/developer/blockchain/blockchain_quickguide_tutorial.html
How come sometimes I need to import Crypto and sometimes I don't? i.e. sometimes just the "from Crypto.Hash import RSA" works without importing Crypto and sometimes I do have to import Crypto. Also curious why don't you use RSA 2048 instead of 1024? Isn't it more secure?
It is recommended that you use RSA 2048.
Computers are getting stronger, key lengths less than 2048 bits are now considered deprecated by the NIST.
Key use prediction: 1024-bit is OK until 2010, then 2048-bit until 2030, then 3072-bit after that.
Please keep in mind, the increase in key length corresponds to an exponential increase in CPU usage.
2048 bit key lengths can take upwards of 4 times as much CPU usage compared to 1024 bit key lengths.
ok and when you write "from Crypto.Hash import RSA" why don't you need to import Crypto since Crypto is a python module? Thanks.
Sorry, do not know the answer.
Is non-repudiation really enforceable under this scheme? Somebody could have had their private key stolen from them.
Please give me the file SHA256, RSA, Random. thank you
wher can i get the python files which you have shown in this video and previous video of cryptography ?