tokens: ['When', 'the', 'MME', 'initiates', 'a', 'reauthentication', 'to', 'create', 'a', 'new', 'EPS', 'security', 'context', 'the', 'messages', 'exchanged', 'during', 'the', 'authentication', 'procedure', 'are', 'integrity', 'protected', 'and', 'ciphered', 'using', 'the', 'current', 'EPS', 'security', 'context', 'if', 'any', 'Both', 'UE', 'and', 'MME', 'shall', 'continue', 'to', 'use', 'the', 'current', 'EPS', 'security', 'context', 'until', 'the', 'MME', 'initiates', 'a', 'security', 'mode', 'control', 'procedure', 'The', 'SECURITY', 'MODE', 'COMMAND', 'message', 'sent', 'by', 'the', 'MME', 'includes', 'the', 'eKSI', 'of', 'the', 'new', 'EPS', 'security', 'context', 'to', 'be', 'used', 'The', 'MME', 'shall', 'send', 'the', 'SECURITY', 'MODE', 'COMMAND', 'message', 'integrity', 'protected', 'with', 'the', 'new', 'EPS', 'security', 'context', 'but', 'unciphered', 'When', 'the', 'UE', 'responds', 'with', 'a', 'SECURITY', 'MODE', 'COMPLETE', 'it', 'shall', 'send', 'the', 'message', 'integrity', 'protected', 'and', 'ciphered', 'with', 'the', 'new', 'EPS', 'security', 'context', 'The', 'MME', 'can', 'also', 'modify', 'the', 'current', 'EPS', 'security', 'context', 'or', 'take', 'the', 'noncurrent', 'native', 'EPS', 'security', 'context', 'if', 'any', 'into', 'use', 'by', 'sending', 'a', 'SECURITY', 'MODE', 'COMMAND', 'message', 'including', 'the', 'eKSI', 'of', 'the', 'EPS', 'security', 'context', 'to', 'be', 'modified', 'and', 'including', 'a', 'new', 'set', 'of', 'selected', 'NAS', 'security', 'algorithms', 'In', 'this', 'case', 'the', 'MME', 'shall', 'send', 'the', 'SECURITY', 'MODE', 'COMMAND', 'message', 'integrity', 'protected', 'with', 'the', 'modified', 'EPS', 'security', 'context', 'but', 'unciphered', 'When', 'the', 'UE', 'replies', 'with', 'a', 'SECURITY', 'MODE', 'COMPLETE', 'message', 'it', 'shall', 'send', 'the', 'message', 'integrity', 'protected', 'and', 'ciphered', 'with', 'the', 'modified', 'EPS', 'security', 'context']