Forward-secure crash-resilient logging device
A logging device configured to store log messages, includes a storage device having a plurality of log entry locations which can be ordered as a sequence, an encryption device configured to generate the encrypted log messages from log messages, an authentication code generator configured to generate an authentication code from the encrypted log message, a key evolving device, a state storage device configured to store state variables for use by the encryption device, the authentication code generator and/or the key evolving device. Furthermore, a verification device configured to verify log entries stored in log entry locations of the storage device is also described. A method for storing log entries in log entry locations of a storage device of a logging device as well as to a method for verifying the integrity of log entries stored in log entry locations of a storage device is also described.
1. A method of verifying integrity of log entries stored in log entry locations of a storage device, the method comprising:
replaying a pseudorandom generator used to determine log entry locations for storing log entries to determine a log entry location in which a particular log entry is to be stored after a predetermined number of log entries has been stored using a method comprising:
encrypting a log message using a secret to create an encrypted log message;
calculating an authentication code from the secret and the encrypted log message to create a log entry comprising the encrypted log message and the authentication code; and
determining a random one of the log entry locations to become a selected log entry location for storing the log entry;
wherein the selected log entry location is determined by using a pseudo random function,
wherein the log entry locations are organized as a numbered sequence, in that only as many log entry locations are used as there are log entries and dummy log entries to be stored and in that an unbroken sequence of log entry locations is used to store the log entries and the dummy log entries, and
verifying integrity of the log entry stored in the log entry location previously determined by verifying the authentication code stored together with the encrypted log message.