The methodology for this framework rates network assurance based on the vulnerability of the transmission technologies to the network attack types described in . This level of vulnerability has then been associated with the information security classification levels defined in the QGISCF, as shown in table 1 below. Information security classification level (ISCL) PUBLIC UNCLASSIFIED IN-CONFIDENCE PROTECTED HIGHLY PROTECTED NTSAL-0 NTSAL-1 NTSAL-3 NTSAL-4 Network transmission security assurance level (NTSAL) Table 1: NTSAL to Information security framework The uses vulnerability as a generic means to provide guidance on securing classified information to the appropriate assurance level during transmission. Attacker ability to execute Outline of protection mechanisms Confidentiality protection Integrity protection Attachment control NTSAL-4 Provides minimal exposure to Extremely computationally difficult and very low probability for even international espionage organisations. Information and cipher keys protected by very strong data encryption. Message authentication integrity with message replay protection. Trusted validation of very strong entity identification and authentication controls restricting attachment to the network. NTSAL-3 Provides low exposure to Computationally difficult requiring a highly sophisticated attack requiring cryptographic skill and resources. Information and cipher keys protected by strong data encryption. Message authentication integrity provided. Strong entity identification and authentication controls restricting attachment to the network. Provides moderate exposure to A fair degree of specialised skill needed for the majority of would be attackers, providing moderation protection Information in the clear on a low vulnerability medium or via standard grade encryption over a shared/public domain network. Basic message integrity checking provided. Basic entity authentication controls or device based access control. NTSAL-1 or 0 Potential to be thwarted by an unskilled attacker Shared access medium, data sent in Basic or no message error checking – little to No specific prevention against unauthorised
Zone two Unrestricted employee and contractor access with restricted public access. Storage of information and physical assets with a classification up to is permitted. (The outer perimeter of Zone Two may move to the building or premise perimeter out of hours if exterior doors are secured.) Normal agency office environments. Normal out-of-office or worksites where the agency has control of access to the part of the site used for agency business Interview and front-desk areas where there is segregation of staff from clients and the public. Vehicle-based work where the vehicle is fitted with a security container, alarm and immobiliser. Exhibition areas with security controls and controlled public access. Zone Three Limited employee and contractor access with escorted or closely controlled visitors only. If security classified information is held, all employees with ongoing access are to hold a security clearance at the highest level of the information they access in the Zone. Storage of information or physical assets of with a classification up to PROTECTED is permitted. Security areas within agency premises with additional access controls on staff. Areas used to store art works or items of cultural significance when not on display. Court rooms. Zone Four Strictly controlled employee access with personal identity verification as well as card access. Only contractors and visitors with a need to know and closely escorted given access. If security classified information is held, all employees with ongoing access are to hold a security clearance at the highest level of the information held in the Zone. Storage of information or physical assets of with a classification up to HIGHLY PROTECTED is permitted. Security areas within agency premises with additional access controls on staff. Exhibition areas for very valuable assets with specific item asset protection controls. Areas used to store art works or items of cultural significance when not on display.
Cryptographic algorithms This appendix provides an overview of the type of cryptographic algorithms used in transmission security, and guidelines on how they should be used. Public key algorithms Public key algorithms are an asymmetric cipher mechanism with two different keys. One key is made public and the other is kept private. Data encrypted with one key can only be decrypted by the other and vice versa. Typically, the public keys are given out and the private key is kept secret and protected. Public key algorithms are typically used in authentication or for securely exchanging cryptographic keys over an un-trusted network. Public key algorithms Description and recommendations Conditions of use Diffie-Hellman (D-H) Agreeing on encryption session keys. The modulus MUST be at least 1024 bits. Elliptic Digital Signature Algorithm (ECDSA) Agreeing on encryption session keys. The field/key size MUST be at least 160 bits. Elliptic Curve (ECDH) Digital signatures The size MUST be at least 160 bits. Digital Signature Algorithm (DSA) Digital signatures. The modulus MUST be at least 1024 bits. (RSA) Digital signatures. Passing encryption session keys or similar keys. The modulus MUST be at least 1024 bits. Note: The public keys used for passing encryption session keys MUST be different to the keys used for digital signatures. Table 7: Public key algorithms Symmetric key algorithms Symmetric key algorithms rely on both communicating entities sharing a secret key. Unlike public key algorithms, the same key is used for encryption and decryption. Symmetric algorithms are mostly used for the bulk encryption once each has been authenticated and the shared key has been securely exchanged. Symmetric key algorithms are used for encrypting the bulk transmission of data as they operate much faster than public key algorithms. Symmetric key algorithms Description and recommendations Conditions of use Advanced Encryption Standard (AES) A encryption standard developed by the NSA to gradually replace 3DES. Endorsed by the NIST and FIPS information standards. AES supports key lengths of 128, 192, 256 and 512 bits, and uses a 128 bit block.
(TLSv1.2) Spoofing/Alteration Medium Low, Very Low Attachment Medium Low, Very Low 802.11i + 802.1x Eavesdropping Medium Low Spoofing/Alteration Medium Low Attachment Medium Low Wi-Fi Protected Access (WPA2) + 8021.x Eavesdropping Medium N/A Spoofing/Alteration Medium N/A Attachment Medium N/A SSH-2 with PKI authentication Eavesdropping Medium Low Spoofing/Alteration Medium Low Attachment Medium Low S/MIMEv3 Eavesdropping Medium Low Spoofing/Alteration Medium Low Attachment Medium Low Open PGP Eavesdropping Medium Low Spoofing/Alteration Medium Low Attachment Medium Low Table 11: Cryptographic protocol vulnerability assessment