@conference {uvigo:visible,
	title = {Visible Encryption: Using Paper as a Secure Channel},
	booktitle = {Security and Watermarking of Multimedia Contents},
	series = {Proc. of SPIE},
	volume = {5020},
	year = {2003},
	address = {Santa Clara, USA},
	keywords = {2-D-Bar-Codes, data-hiding, print-\&-scan, Two-dimensional-modulations, visible-encryption},
	author = {Norberto Degara-Quintela and Fernando P{\'e}rez-Gonz{\'a}lez},
	editor = {Ping W. Wong and Edward J. Delp}
}
