Query Reagrding DER Signature

Question

(For Bitcoin TestNet Only)

I am working on Signed Transaction which consists More than One Inputs and More than One Outputs (Unsigned HEX Data).

after that i have generated two DER Signature of both Inputs. But First input DER Signature is not Right, where as Second Input DER Signature is Right.

This is Serialized Data for Input 1 and Address Node: 0200000002103f960104b258426cf61dac8d8287cc993efd56f2ad0ebe8d279d71a3998343000000001976a9145ecef50c9b41f9714c3aa9c8198a45355e55480688acfdffffff103f960104b258426cf61dac8d8287cc993efd56f2ad0ebe8d279d71a39983430100000000fdffffff02d1d10000000000001976a9142be8cc719306b87e23bc9f1478cb77440adac44288ac60182300000000001976a9141d71b20b5123b6a559693e8ad871015a9a19947d88ac26ec180001000000

Chain Code : b6e74e646730dc4a0d00006e648322325d21f9ffcc182ac7f41dc6a8bc327f50

Private Key : 2f6a4ea2eb8fdfbfd33008b767b4b7b86f2421278c5c1e4dd03353a080b956bb

Public Key : 02f8419833c76c016478a2d3f10ee9399c3c2c0af301e616ff54581cd7ee344d8b strSHA256Digest_SerializeData [0]: 65396c41a751254177c73c26f30c25ea4a683de0977acccec5e61d89473ed7d8

Signed Message [0]: ca92cfde70a674377c2e3cfcc46031ee50103e5036b7890930c3e1fa924105c721a71ad5121d7b84f9dd14900ab836bd36ab7959483fe9c6d4dcab7a1a152b77

DER Signature Message [0] (Message Size :71) : 3045022100ca92cfde70a674377c2e3cfcc46031ee50103e5036b7890930c3e1fa924105c7022021a71ad5121d7b84f9dd14900ab836bd36ab7959483fe9c6d4dcab7a1a152b77

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This is Serialized Data for Input 2 and address Node: 0200000002103f960104b258426cf61dac8d8287cc993efd56f2ad0ebe8d279d71a39983430000000000fdffffff103f960104b258426cf61dac8d8287cc993efd56f2ad0ebe8d279d71a3998343010000001976a914c4c6b6dc0e7d63a2441d89df9e088a8b1e06655f88acfdffffff02d1d10000000000001976a9142be8cc719306b87e23bc9f1478cb77440adac44288ac60182300000000001976a9141d71b20b5123b6a559693e8ad871015a9a19947d88ac26ec180001000000

Chain Code : 1d2580001e84096d110da4bb2617d93f8210b06163410660ee4b5f7330b849ef

Private Key : ae953391f394b83f796dafe29bf2820fc1e91038bea100971465499a9d0be96f

Public Key : 035ad36065a1dd8a74dc473c651cac1c34af6431f6457c634c73bece96522d454f

strSHA256Digest_SerializeData [1]: 3727266237d36b57fb5c343dc0bca40a925072c94947e41b118006983af6efe6

Signed Message [1]: 727937a941b405c4bb3652037b21c5c34714391f30348f8504ca06ea08642fa76509af604cbfcbce6127ae2f94bd7a15b1fc72907409354ae2bc3bb4074c83aa

DER Signature Message [1] (Message Size :70) : 30440220727937a941b405c4bb3652037b21c5c34714391f30348f8504ca06ea08642fa702206509af604cbfcbce6127ae2f94bd7a15b1fc72907409354ae2bc3bb4074c83aa

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This is Final Outcome Signed Data (From My code) : 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

And This is Electrum Signed Data : 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The Only difference between Above Two Signed Message is DER Signature of Input 1 :

DER Signature of Input 1 (My Code) : 4730440220727937a941b405c4bb3652037b21c5c34714391f30348f8504ca06ea08642fa702206509af604cbfcbce6127ae2f94bd7a15b1fc72907409354ae2bc3bb4074c83aa

DER Signature of Input 1 (Electrum) : 47304402201979b4849549868208a9098a75e78ef34bef3f17d57d032844fd48ce1fbfeff4022001129ec9fa472bb7be4a466f4bd49d127195618f7d25211506d15653f642258f

Please Suggest, 1. Please let us know if i am doing anything wrong ? 2. Why DER Signature of Input1 is different ? even if DER signature of Input2 is fine with the same logic .

Answer 1

You've used the wrong key to sign the first input. You are using the private key for the second input in the first input, so you are getting a different signature. Using the correct key for the first input, I get the same signature as Electrum does. If I use the key for the second input, I get the signature that you got.

Also, just an FYI, you've constructed your first input incorrectly in your final transaction. You have the second input's signature in the first input.

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Specifically:

The private key for input 1 is

2f6a4ea2eb8fdfbfd33008b767b4b7b86f2421278c5c1e4dd03353a080b956bb

Using this to sign the message digest of

65396c41a751254177c73c26f30c25ea4a683de0977acccec5e61d89473ed7d8

results in the signature

304402201979b4849549868208a9098a75e78ef34bef3f17d57d032844fd48ce1fbfeff4022001129ec9fa472bb7be4a466f4bd49d127195618f7d25211506d15653f642258f

which is the signature that Electrum made for input 1.

The private key for input 2 is

ae953391f394b83f796dafe29bf2820fc1e91038bea100971465499a9d0be96f

Using that private key to sign the same message digest, I get the signature

3045022100ca92cfde70a674377c2e3cfcc46031ee50103e5036b7890930c3e1fa924105c7022021a71ad5121d7b84f9dd14900ab836bd36ab7959483fe9c6d4dcab7a1a152b77

which is the signature that you got for input 1.

Therefore, you have mistakenly used the private key for input 2 to sign input 1.