A method for restoring a distributed secret key from a backup storage, the method comprising the steps of: - generating an original secret key and distributing the original secret key among two or more servers, each server thereby holding a share of the original secret key and none of the servers holding all shares of the original secret key, - a first server creating a backup, the backup containing at least the share of the original secret key which is held by the first server, - the servers refreshing the original secret key at least once, where each refresh comprises the steps of: - the servers generating a refreshed distributed secret key and a distributed difference between the previous secret key and the refreshed secret key, each server holding a share of the difference, and the difference constituting a sharing of zero, and the servers discarding their shares of the previous secret key, - each server generating a secret version of its share of the difference and sharing the secret version with at least some of the other servers, and - each server generating an accumulated secret version of the shares of the difference received from the other servers based on the received secret versions of the shares of the difference and previous accumulated secret versions, - the first server restoring its share of the original secret key from the backup and requesting the accumulated secret version of its share of the difference from the other servers, - at least some of the other servers providing the accumulated secret version of the first server's share of the difference to the first server, and - the first server restoring its share of the latest refreshed secret key from the received accumulated secret version and the restored share of the original secret key. - generating an original secret key and distributing the original secret key among two or more servers, each server thereby holding a share of the original secret key and none of the servers holding all shares of the original secret key, - a first server creating a backup, the backup containing at least the share of the original secret key which is held by the first server, - the servers refreshing the original secret key at least once, where each refresh comprises the steps of: - the servers generating a refreshed distributed secret key and a distributed difference between the previous secret key and the refreshed secret key, each server holding a share of the difference, and the difference constituting a sharing of zero, and the servers discarding their shares of the previous secret key, - each server generating a secret version of its share of the difference and sharing the secret version with at least some of the other servers, and - each server generating an accumulated secret version of the shares of the difference received from the other servers based on the received secret versions of the shares of the difference and previous accumulated secret versions, - the servers generating a refreshed distributed secret key and a distributed difference between the previous secret key and the refreshed secret key, each server holding a share of the difference, and the difference constituting a sharing of zero, and the servers discarding their shares of the previous secret key, - each server generating a secret version of its share of the difference and sharing the secret version with at least some of the other servers, and - each server generating an accumulated secret version of the shares of the difference received from the other servers based on the received secret versions of the shares of the difference and previous accumulated secret versions, - the first server restoring its share of the original secret key from the backup and requesting the accumulated secret version of its share of the difference from the other servers, - at least some of the other servers providing the accumulated secret version of the first server's share of the difference to the first server, and - the first server restoring its share of the latest refreshed secret key from the received accumulated secret version and the restored share of the original secret key.