Steganography is a technique that conceals the very existence of communication by means of hiding secret messages in innocuous cover objects. We previously developed a steganographic method that uses standard MIDI files (SMFs) as cover objects. Our method could conceal the secret messages in SMFs without changing their sound. We also investigated the effectiveness of our method against steganalysis. This steganalytic research revealed that files embedded using our method are vulnerable to detection, because stego SMFs lose the imprints borne by sequencers. In this study, we describe two improved methods of steganography that enable even stego SMFs to keep the sequencer's imprint. As a result, we improved the resistance of SMFs against steganalysis but there was a slight reduction in the embedding rate.

We describe a scheme of secret communication over the Internet utilizing the potentiality of the TCP/IP protocol suite in a non-standard way. Except for the sender and the receiver of the secret communication it does not need any entities installed with special software. Moreover it does not require them to share any key beforehand. Such features of the scheme stem from the use of IP datagrams with spoofed source addresses and their related error messages for the Internet Control Message Protocol (ICMP) induced by artificial faults. Countermeasures against IP spoofing are deployed in various places since it is often used together with attacks such as distributed denial of service (DDoS) and SPAM mailing. Thus we examine the environment where the scheme works as an intention and also clarify the conditions to obsolete the scheme. Furthermore we estimate the amount of secretly communicated data by the scheme and storage requirements for the receivers and those for the observers who monitor the traffic to detect the very existence of such a secret communication. We also discuss various issues including the sender anonymity achieved by the scheme.