The objective of eSign service is to offer on-line service to citizens for instant signing of their documents securely in a legally acceptable form. Two major challenges involved are (a) authentication of the user and (b) Trusted method of signing. Aadhaar based authentication is carried out to address the first challenge and Public Key Infrastructure (PKI) is used to securely sign the user document and establish the trust. e-Hastakshar offers on-line platform to citizens for instant signing of their documents securely in a legally acceptable form, under the Indian IT Act 2000 and various Rules and Regulations therein. Using e-Hastakshar App, an Aadhaar holder can electronically sign a form/document anytime, anywhere, using device such as Personal Computer or Laptop or Mobile. Through e-Hastakshar, C-DAC offers hassle-free fully paperless citizen services and convenience to users. C-DAC utilizes service of Unique Identification Authority of India (UIDAI) for on-line authentication and Aadhaar eKYC service. e-Hastakshar service supports both One Time Password (OTP)/ToTP and Biometric (Fingerprint/Face) based modes of authentication for leveraging eKYC service of UIDAI.