The key is in Hexadecimal

74 68 65 20 6B 65 79 20 69 73

Character Breakdown

Char	Hex	Decimal
t	0x74	116
h	0x68	104
e	0x65	101
	0x20	32
k	0x6B	107
e	0x65	101
y	0x79	121
	0x20	32
i	0x69	105
s	0x73	115

The key is in Other Codes

The key is in Morse Code The key is in Binary The key is in Braille The key is in NATO Alphabet