Subliminal channels are covert channels established in cryptosystems such as digital signatures and authentication systems by exploiting the inherent randomness of the cryptosystems and are used to hide secret information. Subliminal channel is a serious threat to sensitive systems with high-level security. The state-of-the-art security requires subliminal channels to be detected and if possible prevented. A subliminal-free variant of ECDSA using interactive protocol is designed so that the session key in ECDSA is completely subliminal-free. In the interactive protocol, the signer and the warden who detects each data sent by the signer are the two participants. And at the end of the protocol the warden finishes the signer's signature but he can't forge the signer's signature.