Digital Signatures

• Only you can sign, but anyone can verify.
• Operations of the API for Digi Sign:

1. (sk,pk) := generateKeys(keysize)
 
sk: Secret Signing Key 
pk: Public Verification Key 
 
2. sig := sign(sk, message)
 
3. isValid := verify(pk, message, sig)

Requirements for Signatures

“valid signatures verify”

verify(pk, message, sign(sk, message)) == true

“can’t forge signatures”

adversary who: 
			knows pk
			gets to see signatures on messages of his choice
can't produce a verifiable signature on another message

Bitcoin uses Elliptic Curve Digital Signature Algorithm (ECDSA) — Good randomness is essential

Public Keys As Identities (Decentralization)

• Each pair of Public and Secret Key (pk, sk) is considered as an Identity/Address.

• Anybody can make as many identities as they want, no central point of coordination.

Privacy

• Addresses are not connected to the real word identity
• But observer can link together an address’s activity over time, making inferences.