The present invention refers to new binding proteins based on di-ubiquitin modified in 12, 13, or 14 positions selected from positions R42, I44, H68, V70, R72, L73, R74, K82, L84, Q138, K139, E140, S141, and T142 of di-ubiquitin and being able to bind specifically with high affinity to selected targets. Furthermore, the invention provides a method for the generation of said binding proteins. In addition, libraries encoding for said binding proteins based on di-ubiquitin muteins modified in 12, 13, or 14 positions selected from R42, I44, H68, V70, R72, L73, R74, K82, L84, Q138, K139, E140, S141, and T142 are provided.