jsteg is a package for hiding data inside jpeg files, a technique known as steganography. This is accomplished by copying each bit of the data into the least-significant bits of the image. The amount of data that can be hidden depends on the filesize of the jpeg; it takes about 10-14 bytes of jpeg to store each byte of the hidden data. Example: // open an existing jpeg f, _ := os.Open(filename) img, _ := jpeg.Decode(f) // add hidden data to it out, _ := os.Create(outfilename) data := []byte("my secret data") jsteg.Hide(out, img, data, nil) // read hidden data: hidden, _ := jsteg.Reveal(out) Note that the data is not demarcated in any way; the caller is responsible for determining which bytes of hidden it cares about. The easiest way to do this is to prepend the data with its length. A jsteg command is included, providing a simple wrapper around the functions of this package. It can hide and reveal data in jpeg files and supports input/output redirection. It automatically handles length prefixes and uses a magic header to identify jpegs that were produced by jsteg. A more narrowly-focused command named slink is also included. slink embeds a public