| KEY | Cryptographic key, bits [31:0]
This write-only bitfield contains the bits [31:0] of the AES encryption or decryption key, depending on the operating mode:
- In Mode 1 (encryption), Mode 2 (key derivation): the value to write into the bitfield is the encryption key.
- In Mode 3 (decryption): the value to write into the bitfield is the encryption key to be derived before being used for decryption.
The SAES_KEYRx registers may be written only when KEYSIZE value is correct and when the SAES peripheral is disabled (EN bit of the SAES_CR register cleared). A special writing sequence is also required, as described in KEYVALID bit of the SAES_SR register. Note that, if KEYSEL is different from 0 and KEYVALID = 0, the key is directly loaded to SAES_KEYRx registers (hence writes to key register is ignored and KEIF is set).
Refer to Section 32.4.16: SAES key registers on page 1758 for more details.
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