tility Power Rectifier BAttery Charge Gate Battery Bank FIGURE 97.2 Uninterruptible power system. is Halon fire suppression(although Halon use is now being replaced because of environmental concern). Note that some of the natural threats can also be adversary-caused Since there is potential (in spite of protection) for a loss, contingency planning is essential. This includes provisions for software backup(usually off-site hardware backup(e.g, using reciprocal agreements, hot sites, or cold sites [Cooper, 1989]), and disaster ecovery, guided by a structured team that has prepared through tests(most typically simulated) An example of power protection technology is the widely used uninterruptible power system(UPS).An online UPS implementation is shown in Fig. 97. 2. Utility power is shown passed through a switch to a rectifier and gated to an inverter. The inverter is connected to the critical load to be protected. In parallel, continuous charge for a battery bank is provided. Upon loss of utility power, the battery bank continues to run the inverter, thereby furnishing power until graceful shutdown or switching to an auxiliary engine generator can be accom plished. The switch at the lower right protects the UPS by disconnecting it from the load in case of a potentially catastrophic(e.g, short)condition. Cryptology Cryptology includes techniques for securely hiding information (encrypting) from all but intended recipients, for authenticating messages, and for digital signatures, all through the use of ciphers(cryptosystems)[ Simmons, 1992]. It also includes techniques for deducing at least a subset of encrypted information( cryptanalysis)without the privileged knowledge possessed by the intended recipients. Cryptanalysis knowledge is an important asset evelopment of cryptosystems. An example of a contemporary measure of cryptanalysis resistance is putational complexity, which can be applied to measure the inherent difficulty of numeric cryptanalysis processing for some cryptosystems. Figure 97.3 shows the main components of cryptology. The information to be protected is called plaintextcleartext), and protected information is called ciphertext. Adversaries can assively obtain ciphertext, or they might actively interrupt the communication link and attempt to spoof the information recipient. Some of the objectives of encryption are secrecy, authentication(assurance to recipient of sender identity ) and digital signatures(authentication plus assurance to the sender and to any third parties that the recipient ould not have created the signature). As in physical security, assurance of integrity means preventing inter erence in the information-conveying process or, failing that, detecting interference. Here, interference may have the aims of eavesdropping, modifying, introducing misinformation, disavowing messages, and falsely laiming receipt of messages. Almost all cryptosystems involve transformations( frequently made public and almost always assumed to be known by adversaries) of information based on one or more keys(see Fig. 97.3), at least one of which must be kept secret to protect against adversaries. A single-key(symmetric) cryptosystem has only one secret key, c 2000 by CRC Press LLC© 2000 by CRC Press LLC is Halon fire suppression (although Halon use is now being replaced because of environmental concern). Note that some of the natural threats can also be adversary-caused. Since there is potential (in spite of protection) for a loss, contingency planning is essential. This includes provisions for software backup (usually off-site), hardware backup (e.g., using reciprocal agreements, hot sites, or cold sites [Cooper, 1989]), and disaster recovery, guided by a structured team that has prepared through tests (most typically simulated). An example of power protection technology is the widely used uninterruptible power system (UPS). An online UPS implementation is shown in Fig. 97.2. Utility power is shown passed through a switch to a rectifier and gated to an inverter. The inverter is connected to the critical load to be protected. In parallel, continuous charge for a battery bank is provided. Upon loss of utility power, the battery bank continues to run the inverter, thereby furnishing power until graceful shutdown or switching to an auxiliary engine generator can be accom￾plished. The switch at the lower right protects the UPS by disconnecting it from the load in case of a potentially catastrophic (e.g., short) condition. Cryptology Cryptology includes techniques for securely hiding information (encrypting) from all but intended recipients, for authenticating messages, and for digital signatures, all through the use of ciphers (cryptosystems) [Simmons, 1992]. It also includes techniques for deducing at least a subset of encrypted information (cryptanalysis) without the privileged knowledge possessed by the intended recipients. Cryptanalysis knowledge is an important asset in the development of cryptosystems. An example of a contemporary measure of cryptanalysis resistance is computational complexity, which can be applied to measure the inherent difficulty of numeric cryptanalysis processing for some cryptosystems. Figure 97.3 shows the main components of cryptology. The information to be protected is called plaintext (cleartext), and protected information is called ciphertext. Adversaries can passively obtain ciphertext, or they might actively interrupt the communication link and attempt to spoof the information recipient. Some of the objectives of encryption are secrecy, authentication (assurance to recipient of sender identity), and digital signatures (authentication plus assurance to the sender and to any third parties that the recipient could not have created the signature). As in physical security, assurance of integrity means preventing inter￾ference in the information-conveying process or, failing that, detecting interference. Here, interference may have the aims of eavesdropping, modifying, introducing misinformation, disavowing messages, and falsely claiming receipt of messages. Almost all cryptosystems involve transformations (frequently made public and almost always assumed to be known by adversaries) of information based on one or more keys (see Fig. 97.3), at least one of which must be kept secret to protect against adversaries. A single-key (symmetric) cryptosystem has only one secret key, FIGURE 97.2 Uninterruptible power system