An encrypted hash that is generated to verify the validity of a transaction; it verifies that whoever created the transaction actually owns and is able to spend the relevant coins.

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How do I get hash to verify transaction?

If I have the public key and signature for a transaction how do I get the hash value that is used in verify(hash, sig, pubkey). I want to know how to work backwards from a raw transaction to get it, ...
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23 views

How to extract the signature of a transaction using bitcoinj

I am trying to extract the signatures from a transaction. What is the best way to do this given a com.google.bitcoin.core.Transaction object I just received from the network?
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2answers
42 views

How can someone verify the signature of a Bitcoin ECDSA signature without knowing the signer's public key?

I understand how ECDSA exactly works and for verification of a signature, the public key of the signer is required. But in Bitcoin, public key is double hashed and the only information the receiver ...
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1answer
69 views

Problems with deterministic ECDSA based on RFC6979 in Bitcoin

Generating random number k in elliptic curve is crucial and in any transactions signature in Bitcoin, random number k is required to compute a point k*G. If this k is chosen not randomly, it instantly ...
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65 views

Multisig vs Multi input transaction signing

Let's say we have a 2 of 2 multisig address that we want to spend from, so the transaction should be signed by both of the private keys. Now let's say we have a transaction with two inputs, so once ...
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79 views

How to find Z value of multisig transaction?

for example this transaction: http://2coin.org/txinfo.aspx?txid=6c3dc603da32bba3f56f2b33053aaf0f0f17322386c0c6846786bffe49f6ef22&cur=BTC Script not of right size to be a scriptSig, expecting 2 ...
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2answers
54 views

For what purposes do we need “Sign message”?

I got a simple but straight question: Why do we need "Sign message". Also give explanations and examples.
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1answer
73 views

How do we verify the signature on a raw transaction using Bitcoinj?

I managed to create a raw tx using Bitcoinj but not able to figure out how to verify its signatures. Assuming I know the addresses corresponding to the (supposedly) unspent outputs used as inputs to ...
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1answer
112 views

What are the implications of Schnorr signatures?

Adam Back (adam3us) explained in March, 2014, but it is all math. There's another short post with advantages, though. This answer on crypto.SE claims that Bitcoin considered using Ed25519 which is ...
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1answer
35 views

Double Counting SigOps to Prevent CPU Exhaustion Attacks

In the bitcoin v0.9.3 source: https://github.com/bitcoin/bitcoin/blob/v0.9.3/src/main.cpp ConnectBlock() calls CheckBlock() as one of the first things it does. ...
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1answer
17 views

Is the a library for generating signatures and transactions for scrypt coins?

I'm looking for a library similar to this bitcoin one but that works with scrypt based coins.
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55 views

Why does txID generation consider signatures?

I've been reading a lot about transaction malleability, and noticed that the only way to achieve it is by altering the transaction signature/s. Why does the protocol even consider the signature in ...
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1answer
86 views

How to specify ECDSA nonce used in bitcoin signing code?

Below is the CECKey::Sign() code (v0.9.3). bool Sign(const uint256 &hash, std::vector<unsigned char>& vchSig) { vchSig.clear(); ECDSA_SIG *sig = ECDSA_do_sign((unsigned ...
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1answer
49 views

Why would sending a raw transaction from a different node fail?

When I make a transaction spending an output on one machine (sending it to another locally owned address), and then broadcast it on the same machine, it all works fine, as below. (NODE A) $ ...
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1answer
74 views

If I am spending multiple inputs from the same address, must I provide a signature for each input?

Suppose I have two inputs belonging to the same address. Do I need to provide a signature script for each input that proves that I own it? Wouldn't that waste space? Also, in the standard client, ...
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2answers
215 views

How does the ECDSA verification algorithm work during transaction

I understand the basic concept ECDSA where if Bob wants to sign a message it generates a random number n, multiply it with the secp256k1, r = the x value , s = (H(x)dr)*n^-1 mod q. Also the ...
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1answer
39 views

What is the algorithm used to sign data within Nxt?

I understand that Nxt uses Curve25519 to generate pubkeys for user accounts, however, I can't find a reference that states what which signing algorithm/process is used for transactions and blocks. ...
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1answer
56 views

How many Secp256k1 signatures exist for a piece of data?

ECDSA signatures are not deterministic. That is, random information is used in calculating the signature for a piece of data. Approximately how many unique signatures exist for a piece of data? ...
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1answer
226 views

How to sign bitcoin transaction with 'bitcoind' and non-bitcoind-wallet private key?

My Target I want to create and sign bitcoin transactio using 'bitcoind' and 'bitcoin-cli' only. But the private key is unrelated to 'bitcoind' built-in wallet. That is, private / public key pair was ...
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1answer
50 views

Is it possible to create a transaction with 2txin and 2txout?

Is it possible to create a transaction with 2txin and 2txout? If it is possible, then how does one sign this transaction? Or do I have to create two separate transactions? 1txin 1txout and 1txin ...
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1answer
59 views

Why does re-signing a message in bitcoin-qt produce a different hash

I just noticed that if you repeatedly sign the same message in bitcoin-qt, the signature changes. Why is this?
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3answers
1k views

ECDSA Signature and the “z” value

The following link contains details on how to reverse the ECDSA signature if given two identical "R" values. http://www.nilsschneider.net/2013/01/28/recovering-bitcoin-private-keys.html I have read ...
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2answers
150 views

What should I say when I “sign” a message, to prove that I own an address?

This reddit thread discusses a user who lost some coins and is trying to prove that he owns that address. There was a question in how he signed, and what he signed in the message fields, since it's ...
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2answers
133 views

Can Bitcoin scripting be used for double spending attacks?

A standard Bitcoin transaction deposits coins into an address and then, using Bitcoin's scripting language, states that whoever wants to spend this output must be in possess of the private key ...
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signing colored assets to identify worthwhile assets

With colored coin and similar solutions, anyone can create an asset. Using counterparty as an example, this gets out of control very quickly with no way to determine "good" assets easily ...
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128 views

What is a step by step way to insert data in OP_RETURN?

I was following https://bitcointalk.org/index.php?topic=453086.0 for creating a message in OP_RETURN. I am able to decode my raw transaction, but on signrawtransaction it gives error: ...
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95 views

Can you always derive a public Bitcoin address from a message and a random signature?

Let's say my Bitcoin address is 1Nu5mzpUD9A7daZ76QJEsBfkBjCWVLh7pJ and I sign the message random-challenge with its private key. The result is : ...
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1answer
171 views

Are public keys included in signatures?

I can't easily and quickly determine from these wiki pages, 1 and 2, if the public key is included in the signed message. Are public keys included in the signed message, or are they transmitted ...
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1answer
60 views

Bitcoind need blockchain to sign transaction

I'm trying to sign a transaction using bitcoind via rpc. Here is the request I send. signrawtransaction ...
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1answer
90 views

Verification of transaction once trasaction is broadcasted

I have few doubts regarding verification of transaction and am trying to find answers from last few days. I agree similar post exist in this portal but I am not getting satisfactory answer for my ...
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1answer
33 views

Can I sign and redeem many outputs at the same time? (shrink the size of a tx Input)

I'm looking at this transaction that is redeeming many historical outputs from the same address. When I look at the blockchain, it seems pretty clear there is redundancy here of the public key being ...
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47 views

Bitcoin Qt message signature construction

I'm trying to construct the message verification signature of bitcoin qt in python. I'm able to compute the couple (r,s) of the signature, but, even I'm not able to find the correct way to encode it ...
2
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2answers
89 views

Are Bitcoin signatures currency specific?

I am wondering whether signatures for Bitcoin-like currencies are currency specific, or given one program that can sign a Bitcoin raw/JSON transaction one can create valid signatures for other coins ...
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1answer
168 views

signrawtransaction - Which private key from BitAddress.org?

I am trying to do multisignature addresses and when it comes time to spend the funds, I am getting stuck. If I create a 2 of 3 multisignature address using 3 public keys that I generate locally, then ...
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1k views

SignRawTransaction - What is scriptPubKey and redeemScript? [SOLVED] [closed]

Let me talk about how I got to the situation I'm in right now. I am using PHP and the JSON library to control bitcoind. And doing so..... I created a multisignature address requiring 2 of 3 ...
8
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3answers
190 views

Tx Malleability: Why is the Script not included in the Signed Hash?

Sipa lists sources of tx malleability here: https://gist.github.com/sipa/8907691 It is clear to me how a change in the signature itself or the signature formating leads to a different tx hash (1. ...
3
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1answer
100 views

Is there a signature format, or cryptography has *only one* possible S value?

EDIT: This question is not specific to Bitcoin. It's applicable to any other crypto currency that is interested in using a different signature scheme than Bitcoin or the QT reference client. One ...
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1answer
360 views

What's the rationale of using ECDSA instead of RSA?

One major drawback of (EC)DSA is that it requires a good RNG, otherwise the private key may be accidentally exposed. This is also one of the major reasons (I found so far) why no(?) smartcard supports ...
5
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1answer
92 views

Isn't bribe smearing possible because no payee signature is required?

The Bitcoin protocol does not require the payee to sign for a payment; only the payer signs (the payer signs a hash of the payee and payer's public keys). In other words, a payee signature is not ...
2
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1answer
152 views

Multi-Signature Transaction - Verify First Signature is Valid?

Using Gavin Anderson's TwoOfThree.sh Gist located here: https://gist.github.com/gavinandresen/3966071 Is it possible to verify the first "partial" signrawtransaction is valid from the known public ...
4
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1answer
145 views

How to sign non-standard transaction

Consider Testnet transaction 7a438...de03e which has vout[0].scriptPubKey = OP_DUP OP_DROP OP_DUP OP_HASH160 039.....6fe OP_EQUALVERIFY OP_CHECKSIG The script is equivalent to a standard ...
2
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2answers
86 views

Can an attacker steal a very recent tx and alter it, broadcasting a new tx with his address on the output?

I'm reading the technical FAQs on the wiki, and what I don't see is, if I create a transaction with signed prev_outs and new outputs, do I also sign the ENTIRE new tx before broadcasting? I don't see ...
4
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3answers
101 views

How are “message signatures” verified without having access to the public key?

In the bitcoin-qt client you can sign and verify messages using only the public address. Since the public address is a RIPEMD160 hash how is it possible that I can verify a signature since I do not ...
4
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1answer
872 views

parsing bitcoin input and output addresses from scripts

can someone walk me through the process of combining script inputs and outputs to reveal the base58 encoded input and output addresses. take for example, block 728. this has two raw script inputs: ...
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0answers
64 views

Code sample to sign a transaction

I have the 32-bytes double hash of a transaction, a 32-bytes private key, and I would like to sign the hash using the private key. How do I do that using BouncyCastle (or anything, really), in C# or ...
3
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1answer
146 views

Exhaustive technical explanation of signing & verification

I apologize for such a noobish question and am ashamed that I'm not getting this yet, but I can't seem to put together all of the pieces. I've read every question I can find on the subject, the ...
4
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2answers
509 views

How do signatures work?

Just curious, if I send a transaction from one address to another, how do they verify it without knowing my private key?
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1answer
517 views

How to verify the signature of a raw transaction

I know there are many tools to check an ecdsa signature of a bitcoin transaction and I understand the ecdsa algorithm. It takes three inputs, a hash of the transaction, the digital signature and the ...
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2answers
582 views

How to sign a message using Bitcoin private key?

How does one create a proper signature for a given message using Bitcoin private keys? I have an input address of 5JeWZ1z6sRcLTJXdQEDdB986E6XfLAkj9CgNE4EHzr5GmjrVFpf or ...
4
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1answer
236 views

Why use DER encoding for signatures?

A signature in secp256k1 is two 32 byte numbers. DER encoding a signature adds about 6-7 bytes. It also needlessly complicates things (is DER encoding used anywhere else?). In a transaction format ...