Chandra X-ray Observatory and Fermi Gamma Ray Space Telescope analysis of young supernova remnants (SNRs) Cassiopeia A (Cas A) and Tycho were performed to understand the nature of the high energy emission from SNRs and to observationally test the diffuse shock acceleration (DSA) theory. In this study, we present the highest significances of these shell-like and young SNRs in gamma-ray as a strong evidence for cosmic ray accelerators. Gamma-ray analysis of Cas A and Tycho were performed with Fermi-LAT at significances of 26σ and 8σ, respectively. Chandra analyses were performed on the thin filaments from the shells of Cas A and Tycho. Extracted X-ray spectra have been fitted with power-law model predicting the non-thermal emissions. Best fit chi-squared values for the regions from shells of Cas A and Tycho have been presented in the X-ray analyses which are supporting the DSA theory.