Is sharing a signed input safe? Is it possible to decode the private key from a signed input?

For example:



From this signed input hex...

70736274ff0100aa020000000100c1cf8c7b40f04b87c56ca23a2e3c3c28a9d84255a719574298b80dd67cda080000000000ffffffff034e150000000000001976a9148ae7c5cb8ebc6770109657843cfe0d7c7da3d34088ac701700000000000017a91415b962ea5ca3b2c7010a94cc8c9f38d9d76610768700000000000000002c6a2a6f6e2d636861696e2073656e64202331203a3a2046726f6d206e6f6e2d696e697469616c20757365722e0000000000010120e02e00000000000017a914ed7275a0b04b698e104340dce79c68e4c3151cc387220203fc0078213b78f3699e554c36a780edb4fd6172e07ac92278d9441c98567544d848304502210094544806e12ac1a919066ffd7e53544a4576021342ce6444c514c2efc82cada302207678230172386d0cbef3eb9952b71f602456dfc2d9138969120ec234109eb7bd010104160014bafa0e5f7872430905404a42eb9997e54fd7262000000000




Can I get this private key?

cQ4JFq6BKwgvgqQcQK1d1ZNkpjmaDbmf3NJ99zYb9ESEnaPQwy3s
Is it possible to decode the private key from a signed input?


No. Signatures and public keys are meant to be public. In typical use, using a correct implementation of the signing code, it is currently not possible to determine the private key for a signature and pubkey pair.

Signed inputs are not encrypted or obfuscated in any way, so when you broadcast your transaction, everything in the input, including the signature, will be publicly available for anyone to see.



There are some cases where it is possible to determine the private key for a signature and pubkey pair. However these all involve faulty implementations of the signing code. They usually revolve around the use of bad randomness and otherwise failing to produce a random enough number. For the most part though, these failures are rare.