I have managed to create a temporary "fortress" after losing the exchange. Analyzing the position after the game ended, I was able to find a plan for White to breakthrough. After further analysis I was able to find the defense for Black.
My "gut feeling" tells me that White should win anyway but I need help in finding the solution.
Below is the position:
[Title "White to move"] [fen "r7/1kp2p2/1p1p3p/p2Pp1nP/P1R1PpP1/1PP2P2/4K3/R7 w - - 0 1"]
EDITED on July, 21th 2014 :
Since nobody ( not even engines! ) considered option of penetrating on the kingside with the King via light squares, I am submitting lines that can guide others when constructing their answers.
[Title "White to move"] [fen "r7/1kp2p2/1p1p3p/p2Pp1nP/P1R1PpP1/1PP2P2/4K3/R7 w - - 0 1"] 1.b4 c5!? 2.dxc6+ Kc7 3.bxa5 bxa5 4.Rb1! Ra7 $8 5.Kf2! Ne6 6.Kg2! Ng5 ( 6...Nc5 7.Rxc5! dxc5 8.g5!+- Kxc6 ( 8...hxg5? 9.Rb7+ Rxb7 10.cxb7+- ) ( 8...Ra8 9.Rb7+ Kxc6 10.Rxf7 hxg5 11.h6 Kd6 12.h7 Ke6 13.Ra7! Rd8 14.Kh3 Kf6 15.Kg4 Kg6 16.Rxa5+- ) ( 8...f6 9.g6!?+- ) 9.Rb8!+- ) 7.Rb5! f6 ( 7...Ne6 8.g5!+- ) 8.Rb1! $22 Ne6 9.g5!! Nxg5 ( 9...fxg5 10.Rb7+! $8 Rxb7 11.cxb7 Kxb7 12.Kh3+- ) ( 9...hxg5 10.Rb7+ Rxb7 11.cxb7+ Kxb7 12.h6+- ) 10.Rb5! Ne6 11.Kh3 $22 Nc5 ( 11...Ng5+ 12.Kg4+- ) ( 11...Ng7 12.Kg4+- ) 12.Rcxc5!+- dxc5 13.Rb7+ Rxb7 14.cxb7 Kxb7 15.Kg4+-
Based on the above lines, I have tried to "sit in place", and came to the critical position where Black seems to hold:
[Title "White to move"] [fen "r7/1kp2p2/1p1p3p/p2Pp1nP/P1R1PpP1/1PP2P2/4K3/R7 w - - 0 1"] 1.b4 f6 2.bxa5 Rxa5 $8 ( 2...bxa5? 3.Rb1+ Kc8 4.Rbb6! Kd7 5.Rb7+- ) 3.Rcb4 Nf7 4.c4 Nd8 5.Rb5! Rxb5 ( 5...Ra8 6.a5! ) 6.cxb5! $8 Nf7 7.Ra3! Ng5 8.Kd2 Kb8 ( 8...Nf7!? ) 9.Kc2 Kb7 10.Rc3! Nh7 11.Kb3 Nf8 12.Kb4 Nd7 13.a5 bxa5+ ( 13...Nc5!? 14.a6+! $8 Kb8 15.Kc4! Nd7 16.Kd3 Nc5+ $8 ( 16...Nf8 17.a7+!+- ) 17.Ke2 Ka7 $8 ( 17...Na4? 18.a7+!+- ) 18.Kf2 Kb8 $8 19.Kg2 Ka7 20.Kh3 Kb8 21.g5!+- fxg5 $8 22.Kg4 Ka7 23.Kf5 Kb8 24.Rc2!! Ka7 25.Rc1! Kb8 26.Rg1! Nb3 27.Rxg5!! Nd4+ 28.Kg4! Nxb5 29.Rg6 Ka7 ( 29...Nd4 30.Rxh6 b5 31.Rh7! b4 32.a7+! Kxa7 ( 32...Kb7 33.Rxc7+!+- ) 33.Rxc7+ Kb6 34.Rc1+- ) 30.Rxh6 Kxa6 31.Rh7 Kb7 ( 31...Nd4 32.Rxc7+- ) 32.h6 Nd4 33.Rg7+- ) 14.Kxa5
It seems that Black can indeed create an impregnable fortress. Sacrifice with
b6 does not work, and knight will always be able to reach
g5 in time to stop White king from penetrating via
g5 sacrifice. If White sacrifices on
g5 too early, Black will always have
Nf6 and will move around his king, maintaining blockade. Lines where White sacrifices rook on
g5 end bad since Black sacrifices the knight and has won pawn endgame.
I will investigate few more ideas ( like
c5 sacrifice ), before I officially accepting an answer...