# Does every transaction have the same signature?

I want to know whether the bitcoin network generates the same signature for each transaction, because people have only one signature?

No, according to the bitcoin network, the system generates a different digital signature for each transaction. Because the sender generates a digital signature from a transaction message and his private key.

A signature is an intermediary that proves you have a password without seeing the private key due to the math algorithm.

• You're correct that every signature is different and that it is generated using the transaction message and private key. However, I don't understand what that's supposed to have to do with allowing users to generate new keys.
– Murch
Nov 30, 2020 at 18:38
• @Murch I was just giving extra information. However, now I updated my answer. Thanks for mentioning. Dec 1, 2020 at 10:02
• This is much better, but equating a private key to a password is not quite right. How about "A signature proves that you have the private key without revealing anything about the key itself."?
– Murch
Dec 1, 2020 at 13:32

Bitcoin uses the Elliptic Curve Digital Signature Algorithm (ECDSA). While people in the physical world use their unique signature to authenticate when accepting documents or contracts, digital signatures are cryptographic commitments by the owner of a private key corresponding to one specific message (which in this case is the Bitcoin transaction).

As the inputs to the signature generation algorithm are the message and the private key, different messages produce different signatures.

• What's the format of the Bitcoin transaction in the Signature that everyone keeps referring to as a message? Also, aren't some high entropy numbers used in a signature, to keep them different even for the same message from the same address? Thank you. Dec 1, 2020 at 12:26
• Yes, the signature generation additionally requires rolling a random number, the nonce value `k` which is used to derive the r-value. The signature does not include the message, but it commits to the sighash which is a digest of the whole transaction.
– Murch
Dec 1, 2020 at 13:25