Saving in computational cost Clause Samples

Saving in computational cost. With the signature-then-encryption based on ▇▇▇▇▇▇▇ signature and ElGamal encryption, the number of modular exponentiations is three, both for the process of signature-then- encryption and that of decryption-then-veri cation. a a multiplications is computationally equivalent to 1.17 modular exponentiations. Thus with \square-and-multiply" and ▇▇▇▇▇▇'s technique, the number of modular exponentiations in- volved in decryption-then-veri cation can be reduced from 3 to 2.17. The same reduction techniques, however, cannot be applied to the sender's computation. Consequently, the combined computational cost of the sender and the recipient is 5.17 modular exponentia- tions. In contrast, with SCS1 and SCS2, the number of modular exponentiations is one for the process of signcryption and two for that of unsigncryption respectively. Since ▇▇▇▇▇▇'s technique can also be used in unsigncryption, the computational cost of unsigncryption is about 1.17 modular exponentiations. The total average computational cost for signcryption 512 144 72 58% 70.3% 768 152 80 58% 76.8% 1024 160 80 58% 81.0% 1280 168 88 58% 83.3% 1536 176 88 58% 85.3% 1792 184 96 58% 86.5% 2048 192 96 58% 87.7% 2560 208 104 58% 89.1% 3072 224 112 58% 90.1% 4096 256 128 58% 91.0% 5120 288 144 58% 92.0% 8192 320 160 58% 94.0% 10240 320 160 58% 96.0% jhash( )j+jqj+jpj