IoT (Internet of Things) is regarded as a diversified science and utilization with uncommon risks and opportunities of business. So, in this article, a digital signature mobile application (SignOn) is presented where, it provides a cloud based digital signature with a high security to sustain with the growth of IoT and the speed of the life. Different algorithms were utilized to accomplish the integrity of the documents, authenticate users with their unique signatures, and encrypt their documents in order to provide the best adopted solution for cloud-based signature in the field of IoT. Where, ECDSA (Elliptic Curve Digital Signature Algorithm) is utilized to ensure the message source, Hash function (SHA-512) is used to detect all information variations, and AES (Advanced Encryption Standard) is utilized for more security. SignOn is considered as a legal obligated way of signing contracts and documents, keeping the data in electronic form in a secure cloud environment and shortens the duration of the signing process. Whereas, it allows the user to sign electronic documents and then, the verifier can validate the produced signature.