title: How does a public key verify a signature?
body: <p>I am trying to get a better grapple on how public/private keys work. I understand that a sender may add a digital signature to a document using his/her private key to essentially obtain a hash of the document, but what I do not understand is how the public key can be used to verify that signature. </p>
  
  <p>My understanding was that public keys encrypt, private keys decrypt... can anyone help me understand? </p>