A system and method for authentication and digital signatures on memory-only supports, comprising a read-once memory unit storing secret arrays, whose contents are destroyed upon reading, a standard memory unit storing encrypted arrays, tree data authenticating the encrypted arrays to one single public key, and a certificate of the public key issued by a certificate authority. The memory support sends its public key and certificate to a verifier, receives a challenge which is signed by elements from secret arrays in the read-once memory. The verifier system checks the authenticity of the data revealed from the read-once memory by encrypting it and comparing the result to one of the encrypted arrays, and verifies that the encrypted array authenticates to the public key using tree data. Finally, the verifier checks the authenticity of the public key using the certificate.