Initial authentication procedure Sample Clauses

Initial authentication procedure. To mitigate the computation burden of mobile equipment, the encryption is clone in MS side since the public key operation takes Ο (K2) complexity but private key operation takes Ο (K3) complexity with the typical modular exponentiation algorithms used to implement the RSA algorithm (ITU_T, 1993), where K is the number of bits in the modulus. Table 3.1 gives the software speeds of RSA (▇▇▇▇, et al., 1993). RSA goes much faster if we choose a value of e carefully. Therefore, we suggest the exponent value e should be smaller. In order to make use of public key cryptography on the low- computation mobile equipment, the related research can be found in (Belier, Chang & ▇▇▇▇▇▇, 1993). RSA Speeds for Different Modulus Lengths with an 8-bits Public Key(on a SPARC ІІ) 512 bits 768 bits 1,024 bits Encrypt 0.03 sec 0.05 sec 0.08 sec Decrypt 0.16 sec 0.48 sec 0.93 sec Sign 0.16 sec 0.52 sec 0.97 sec Verify 0.02 sec 0.07 sec 0.08 sec In 2003, RSA Laboratories recommends the minimum key length for general data is 1024 bits without any specifying lifetime (▇▇▇▇▇▇▇, 2003). NIST recently recommends 1024 bits for RSA, which is taking into account the lifetime of the data (NIST, 2003). For security concerns and the execution speeds of the public key encryption, we suggest the value of public key length is optimally 1024 bits. Before we describe the common registration phase of the proposed mechanism, we assume the following operations are performed when MS makes a service contract with his/her home network HLR: HLR generates the Public and Private Keys. HLR subscribes (Public Keys) to MS. HLR produces a certificate CertM to public keys and keeps it in its database. HLR writes KHU, IMSI and CertM in SIM/USIM of MS. At first, we consider the scheme that consists of four messages exchange among MS, VLR and HLR. The message flows are indicated in Figure 3.1. The notations in Figure 3.1 are defined as follows: IMSI International Mobile Subscriber Identity KHU, KHP Public/private key pair of HLR KVU, KVP Public/private key pair of SGSN/VLR K ’ The new HLR’s public key KVM Session key shared by the MS and SGSN/VLR KVM’ ƒ(IK, CK): session key between the MS and VLR, the function ƒ may be a simple function. e.g. the XOR of IK and CK. h (KVM, IK ⊕ CK)