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Only top voted, non community-wiki answers of a minimum length are eligible. Questions Tags Users Badges Unanswered. Tag Info users hot new synonyms. Hot answers tagged ecdsa day week month year all. I'll try answering this again in a different way, using small numbers to keep it readable. Willem Hengeveld 1, 8 There are two different encodings used. Everything in the Bitcoin protocol, including transaction signatures and alert signatures, uses DER encoding. This results in 71 bytes signatures on average , as there are several header bytes, and the R and S valued are variable length.
For message signatures, a custom encoding is used which is more compact and Pieter Wuille 40k 2 75 In Bitcoin, for message signatures, we use a trick called public key recovery. The fact is that if you have the full R point not just its How do you derive the private key from two signatures that share the same k value?
If you have two s values s1 and s2 for the same secret key and with the same nonce k and thus the same value r , the following holds: ECDSA r, s encoding as a signature. Or, you can cheat and look at RFC, section 8. If you look at this transaction you can see that one of the signatures is: When the executable in your path, enter this command to generate a private key: I'm not sure what format the web page As you can read here: This makes RSA less Luca Matteis 4, 10 So when you are deducing the k value, it is possible that someone else flipped the sign of s and you will have to undo it.
So, you have to make a list of candidates for k kandidates? David Grayson 3 9. Is libsecpk1 faster than OpenSSL? Yes it's a lot faster. For example from one of the core developers: When the assembly is compiled in which does not require any Jannes 5, 13 Bitcoin private key, location on ECC curve.
The basic elliptic curve operation is addition of points. The operation of applying this addition repeatedly is called the scalar multiplication of a point by an integer. The private key is the 'scalar', the point being multiplied is the 'Generator' point, the result is the public key. Scalar multiplication is basically repeated addition. Let us take "pizza transaction" https: Simple, the sender shows the pubkey when spending from whatever address the bitcoins are in.
As part of the verification, the receiver actually, every node in the network , can verify that the pubkey hashes to the address given and then and only then verifies the signature. Jimmy Song 6, 8 Why use DER encoding for signatures? If it didn't require a hard forking change requiring every wallet and verifying node on the network to upgrade , we'd have changed it long ago. Not any serious efficiency concerns.
Signing is done fairly infrequently for any particular client only a few signatures per transaction usually.
While possible that the signing might take slightly longer to generate the k value, it would not be noticeable, especially considering how infrequently it is used by any one particular client. Schnorr will replace ECDSA, the signing algorithm, but both still use the same elliptic curve and thus the same public and private keys, etc. Regardless, compatibility with ECDSA must be kept too even if Schnorr is used, because otherwise all old nodes would see the schnorr signatures as invalid signatures, and all old transactions would be seen as invalid Why do keys need both X and Y coordinates, if X can be solved for Y using the curve equation?
A private key is just a number modulo the order of the curve. A public key is the X,Y coordinate pair corresponding to that number the private key multiplied by the base point which is a property of the curve used.
If you're talking about public keys: The Y coordinate can indeed be computed from the X coordinate, if you know the How vulnerable is bitcoin to quantum algorithms? In short, yes, Bitcoin would be vulnerable to some variation of Shor's algorithm and quantum computing, as would basically every kind of crypto we use today.
While ECDSA uses the elliptic curve discrete logarithm problem for its security, rather than the prime number factorization problem, you are correct in stating that a variant of Shor's can be used to Good hashes have 4 properties: It's impossible to know that, if you could derive r for arbitrary values then ECDSA would be fundamentally broken.
The best you can do is grind k until you get an r that happens to have a short encoding. For the sake of the exercise: Which programming languages support secpk1? The Bouncy Castle project allows for this and it runs on the Java VM as was mentioned earlier as well as the. An example of using it in C is shown in this blog post. You can use the. NET version from Visual Basic. Frank Geerlings 66 1. Here's a self-contained Python script that does the conversion.
You can check its work by comparing to entering your private key as the "Secret Exponent" at Brainwallet. I took the script from this Bitcointalk thread and stripped out unnecessary stuff like the code to use the public key to sign a message and verify that signature. Converting the Python to Calculating the Z values is quite complicated for the average Joe, so i've made it easier by creating a video tutorial of the steps, https: Sean Bradley 3 4.
Changing the txn format would require a hard fork so it is unlikely that is going to happen but the advantage of pubkey recovery is that it trades storage DeathAndTaxes 7, 1 25 OK, I figured out how to sign the raw Tx using Python ecdsa. I'll step through it: Wizard Of Ozzie 3, 15 How do I convert Public Key x value to y in Python and verify? First, you need to understand what the two formats actually are. The difference between the two is that the compressed format only includes the X value and the parity of the Y value while the uncompressed format includes both the X and Y values.
The 02 at the beginning of How to sign raw transaction given a private key and SHA hash in java. This answer does not attempt to sign a transaction, but simply focuses on successfully calling the sign method of the ECKey class, i. Your post suggests that your private key is given as a WiF so I have taken this as an assumption. Sven Williamson 1, 3 Bitcoin Stack Exchange works best with JavaScript enabled.