1. A MODIFICATION OF THE CRAMER-SHOUP DIGITAL SIGNATURE SCHEME. Authors: CONSTANTIN POPESCU.2. AN EFFICIENT ID-BASED GROUP SIGNATURE SCHEME. Authors: CONSTANTIN POPESCU.3. A PRACTICAL COALITION-RESISTANT GROUP BLIND SIGNATURE SCHEME. Authors: CONSTANTIN POPESCU.4. A MODIFICATION OF THE TSENG-JAN GROUP SIGNATURE SCHEME. Authors: CONSTANTIN POPESCU.5. BLIND SIGNATURE AND BLIND MULTISIGNATURE SCHEMES USING ELLIPTIC CURVES. Authors: CONSTANTIN POPESCU.