Are digital signatures error-proof?

 Digital signatures are a way to make sure that the sender's identity is not mistaken. The sender is confirmed to be who he claims to be. The content signed by the sender too is automatically linked to his identity and he cannot deny that he sent it, because his digital signature appears on it. But if you have never used a digital signature, you may have your own apprehensions.

 As long as the message is hashed and then signed, there is no scope at all for a case of mistaken identity. For example, if you have created a hashed message and then signed it digitally and the document is altered (by anyone, including yourself) in any way, the recipient will fail to match the public key with your private key. This shows that digital signatures by themselves are error-proof not only with respect to identity but also content. Of course, when the verification process fails, you would not be able to know if it was just a transmission error or a forgery attempt.