Automated private key recovery for DNSSEC Colorado State University, CS 681 John Tesch

1. Automated private key recovery for DNSSEC Colorado State University, CS 681 John Tesch

2. Motivation • DNSSEC provides for asymmetric keys but does not address the issue of lost keys. • The key regeneration process may affect performance of DNS servers • Multiple pairs of keys create conflicts among DNS servers

3. Asymmetric keys • The public key is stored in the KEY resource record and is backed up. • The private key is stored and protected in the file system of the DNS server • The public key can be reloaded • The loss of the private key requires a re-computation of a new pair of keys

4. Simplistic Approach • Take the private key, Sprv, and encrypt it with the public key of the parent DNS server, Ppub. m = [Sprv,Ppub] • Provides some redundancy, but still a single point of failure • Can be compromised or lost

5. Our Approach • Take the private key, Sprv, and encrypt it with the public key of the parent, Ppub. m = [Sprv,Ppub] • Divide the encryption, m, into parts or shares. m\n • Distribute and encrypt the shares to subordinate DNS servers (child). • [m/n,Cpub]

6. (k,n)=threshold scheme • A dealer shares a secret key between n parties • Each party receives a share • A group of any k participants can cooperate to reconstruct the shares • No group of k-1 participants can get any information about the secret

7. Algorithm modification • Use Shamir’s (k,n)-threshold scheme • Encrypt the shares with the public keys of the DNS childern • Store the shares on the DNS database as a Resource Record

8. Conclusion • Using our method, private keys can be stored in plain sight. • The use of the (k,n)-threshold scheme allows for voting when recreating the private key • The distribution of the shares cannot be easily traced