News
Ulf Mattsson, Protegrity Corporation: Encryption keys should be protected in memory, on disk and during transport between processes
October 2008 by Marc Jacob
Encryption keys can be protected and encrypted when stored in memory or in databases, and also during transport between systems and system processes. The use of a combination of software cryptography and specialized cryptographic chipsets, called a Hardware Security Module, can provide a selective added level of protection, and help to balance security, cost, and performance needs.
Certain fields in a database require a stronger level of encryption, and a higher level of protection for associated encryption keys. Encryption keys and security metadata should continuously be encrypted and integrity validated – even when communicated between processes, stored or cached in memory. Security data should remain ciphered until needed for use by crypto-services routines. Memory attacks may be theoretical, but cryptographic keys, unlike most other data in a computer memory, are random. Looking through memory structures for random data is very likely to reveal key material. Well made libraries for use as Native Encryption Services go to great efforts to protect keys even in memory. Key-encryption keys are used to encrypt the key while it is in memory and then the encrypted key is split into several parts and spread throughout the memory space. Decoy structures might be created that look like valid key material. Memory holding the key is quickly zeroed as soon as the cryptographic operation is finished.
These techniques reduce the risk of memory attacks. Separate encryption can also be used for different data. These encryption keys can be automatically rotated based on the sensitivity of the protected data. Dedicated Encryption Services are also vulnerable to memory attacks. However, a well made Dedicated Encryption Service runs only the minimal number of services. Since web servers, application servers, and databases have no place on a dedicated cryptographic engine, these common attack points aren’t a threat. This severely constrained attack surface makes it much more difficult to gain the access needed to launch a memory attack. To maintain a high level of security backups contain the encrypted data and only securely encrypted lower level keys.
