37.8.8 Keyword n

Name: KEYWORDn
Offset: 0x0C + n*0x04 [n=0..7]
Reset: 0x00000000
Property: PAC Write-Protection

Bit 3130292827262524 
 KEYWORD[31:24] 
Access WWWWWWWW 
Reset 00000000 
Bit 2322212019181716 
 KEYWORD[23:16] 
Access WWWWWWWW 
Reset 00000000 
Bit 15141312111098 
 KEYWORD[15:8] 
Access WWWWWWWW 
Reset 00000000 
Bit 76543210 
 KEYWORD[7:0] 
Access WWWWWWWW 
Reset 00000000 

Bits 31:0 – KEYWORD[31:0] Key Word Value

The four/six/eight 32-bit Key Word registers set the 128-bit/192-bit/256-bit cryptographic key used for encryption/decryption. KEYWORD0.KEYWORD corresponds to the first word of the key and KEYWORD3/KEYWORD5/KEYWORD7.KEYWORD to the last one.
Note: By setting the XORKEY bit of the CTRLA register, keyword will update with the resulting XOR value of user keyword and previous keyword content.