Attack models Total Brea king Attack The attacker knows the public key. He tries to recover the corresponding secret key. Forgery Attack The attacker knows the public key. He tries to find the signature for a given message Existential Forgery Attack The attacker knows the public key. He tries to find a pair of a message and its signature Chosen Message Attack(CMA) The attacker is able to sign messages but does not know the key used. He tries to perform the(existential) forgery or to obtain the secret key 1515 Attack models • Total Breaking Attack - The attacker knows the public key. He tries to recover the corresponding secret key. • Forgery Attack - The attacker knows the public key. He tries to find the signature for a given message. • Existential Forgery Attack - The attacker knows the public key. He tries to find a pair of a message and its signature. • Chosen Message Attack (CMA) - The attacker is able to sign messages but does not know the key used. He tries to perform the (existential) forgery or to obtain the secret key