Datasheet

GHASH
AUTHDAT +
GF128Mult(H)
GHASH
42.6.3.1.3 Plain text Processing
• Set CTRLB.NEWMSG for the new set of plain text processing.
• Load CIPLEN reg.
• Load (J0+1) in INTVECT register.
• As described in NIST documentation J 0 = IV || 0 31 || 1 when len(IV)=96 and J0 =GHASH
H
(IV || 0 s
+64 || [len(IV)] 64 ) (s is the minimum number of zeroes that should be padded with the Initialization
Vector to make it a multiple of 128) if len(IV) != 96.
• Load plain text in DATA register.
• Set CTRLB.START as 1.
• Wait for INTFLAG.ENCCMP to be set.
• AES Hardware generates output in DATA register.
• Intermediate GHASH is stored in GHASH register and Cipher Text available in DATA register.
• Continue 3 to 6 till the input of plain text to get the cipher text and the Hash keys.
• At the last input, set CTRLB.EOM.
• Write last in-data to DATA reg.
• Set CTRLB.START as 1.
• Wait for INTFLAG.ENCCMP to be set.
• AES Hardware generates output in DATA register and final Hash key in GHASH register.
• Load [LEN(A)]64||[LEN(C)]64 in DATA register and set CTRLB.GFMUL and CTRLB.START as 1.
• Wait for INTFLAG.GFMCMP to be set.
• AES Hardware generates final GHASH value in GHASH register.
42.6.3.1.4 Plain text processing with DMAC
• Set CTRLB.NEWMSG for the new set of plain text processing.
• Load CIPLEN reg.
• Load (J0+1) in INTVECT register.
• Load plain text in DATA register.
• Wait for INTFLAG.ENCCMP to be set.
SAM D5x/E5x Family Data Sheet
AES – Advanced Encryption Standard
© 2019 Microchip Technology Inc.
Datasheet
DS60001507E-page 1422