Dan Boneh David Freeman Jonathan Katz Brent Waters Signing a Linear Subspace: Signature Schemes for Network Coding. 68-87 2009 Public Key Cryptography http://dx.doi.org/10.1007/978-3-642-00468-1_5 conf/pkc/2009 db/conf/pkc/pkc2009.html#BonehFKW09