A second implementation issue with NLTSS related to the security/integrity of its capability as data implementation. This implementation used a password capability model (e.g. see Control by Password). With this model any person or process that could get access to the memory space of a process would have the authority to access the capability represented by the data found in that memory. Some system architects (e.g. Andrew S. Tanenbaum, the architect of the Amoeba distributed operating system) have suggested that this property of access to memory implying access to capabilities is not an inherent problem. In the environment of NLTSS it sometimes happened that people took program memory dumps to others for analysis. Because of this and other concerns, such password capabilities were considered a vulnerability in NLTSS. A design was done to protect against this vulnerability, the Control by Public Key Encryption mechanism. This mechanism wasn't put into production in NLTSS both because of its significant performance cost and because users weren't aware of the vulnerability from password capabilities. Modern advances in cryptography would make such protection for capabilities practical, especially for Internet/Web capabilities (e.g. see YURLs or WideWORD).