Steganography is the art and science of hiding information in ways that prevent its detection. Though steganography is an ancient craft, the onset of computer technology has given it new life. Computer-based steganographic techniques introduce changes to digital covers to embed information foreign to the native covers.Digital steganography involves the hiding of data inside a sound or image file.Steganography works by replacing bits of useless or unused data in regular computer files such as graphics, sound, text, HTML, or even floppy disks with bits of different, invisible information. Steganography strips less important information from digital content and injects hidden data in its place. This is done over the spectrum of the entire image. Computer-based steganographic techniques introduce changes to digital covers to embed information foreign to the native covers. This hidden information can be plain text, cipher text or even images. The hidden information may be communicated in the form of text, binary files, or cipher text. The carrier file can be any graphic or audio files which are at least 8 times the message file. This seminars mainly deals with transform domain embedding techniques and spread spectrum image steganography techniques for digital steganography. The art of detecting, decoding, and altering messages hidden using steganography is called steganalysis.Steganalysis is aimed at detecting and extracting an embedded message from a stego-medium.It is also used for destroy or render unrecoverable that embedded message.