V.1 Security Services

V.2 Security aspects of RPC Mechanisms: –Private-Key-Method (symmetric) „Data Encryption Standard“ (DES) Use of a „Key Distribution Center“ with session keys on the base of private keys Setup of conversation contexts during Binding –Public-Key-Method (asymmetric): RSA Identification and authentication –Identification during Binding –Authentication: Verification of identity of a called object instance and also of server during distribution of session keys

V.3 Encryption Example:System „Kerberos“ with DES used in OSF DCE KeyRequest (C,S) Response ( {{CS}K2, {CS}}K1 ) Message( { }CS, {CS} K2 ) Response ( { }CS ) Message( { }CS) Client C (with key K1) Server S (with key K2) Key distribution center generates CS(S1,S2) CS {CS} K2 CS

V.4 Identification and authentication Identification: –Presentation of a explicit identifier –Assignment and name construction important during Binding (compare with name server) Authentication: –Verification of identity via presentation of a secret identifier –Using of private keys (for instance, from password) –Authentication of the client and of the server via decryption of the (session) key –Key distribution point: authentication service –Additionally: timestamp for prevention of message repeats

V.5 Security aspects of RPC Possible guaranties: –Bugging, modification, call repeat and call initiation prevented –Identity of communication partners guaranteed –tolerable performance losses –Traffic density analysis possible Security classes of DCE RPC –Authentication during Binding –Authentication for each call –Authentication for each packet –Defense against message modification (encrypted control sum) –Full-state encryption

V.6 Asymmetric crypto-method with public keys KD - secret key for decryption KE - public key for encryption nonreversible function F(KD) = KE Client C secret: KD_C public: KE_S KE_S(M) M=KD_C(KE_C(M)) Server S secret: KD_S public: KE_C M=KD_S(KE_S(M)) KE_C(M) Message M transmission Calculation and delivery of private keys

V.7 Authorization Awarding and control of access rights: –Capabilities for Client or –Access control lists for Server RPC Server File Server Name Server MeierMüllerHuber read write - read - write read write „Subject“ „Object“ Access control lists (ACL) Capabilities

V.8 Access control list example usr_obj/.:/sec/principal/Meier: rwid foreign_user/.../firm_z.de/sec/principal/Müller: r--- group_obj/.:/sec/group/Dept_1: rwi- DocumentServer Call: dynamic rights control

V.9 Implementation example -Control of identity of communication partners -Defense against bugging, manipulation, illegal access -Conformant to standards (for instance, DES and IDEA-algorithms) Security Server Client (Cash desk) Account Server Authori- zation Meier: rx Müller:rwx Encrypted transmission Authentication

V.10 Security Service: architecture ACL Manager Application server Authentication protocol ClientSecurity ServiceServer ACL Editor CORBA- runtime-system Security Server Authentication protocol CORBA- runtime-system Application client Authentication protocol Login-Facility CORBA- runtime-system Login-Facility: Password control and generating of a private key Authentication protocol: Processing of distributed authentication ACL Manager: Control of access rights of a client on the server site ACL Editor Definition and manipulation of access rights

V.11 Security Service: Authentication Authenticate “ticket granting ticket” (TGT) with encrypted Client Key Client sends authentication query to the Security Service Security Service generates TGT and encrypts that with Client Key (from password) If client identity is correct, then client can encrypt the TGT (inclusive add-on information) Client sends TGT (newly encrypted) to the Privilege Server (Security Service) This is a proof for correct identity; client receives PAC and is authenticated “ticket granting ticket” (TGT) “privilege attribute certificate” (PAC) Client Security Server (Login- Components) (Privilege Server) 1. Phase: Login

V.12 Security Service: Authentication Requests a Ticket Ticket Authenticated Client requests a Ticket for the application server from the Security Service Security Service controls identity and awards the Ticket Client carries out a call (internal further steps to mutual authentication) ACL Manager of the server controls the authorization ( in ACL contained?) Server carries out the call and delivers the results Communication generally encrypted (however compromise: security vs. performance) Call (Ticket) Answer Client Security Server (Privilege Server) 2. Phase: Call of a server Application server (ACL Manager)