APT:Unwrap

Request

Index Word	Description
0	Header code [0x00470104]
1	Output buffer size
2	Input buffer size
3	Block size
4	Nonce size, size 12 is used if this is >12.
5	(inputbufsize<<4) | 10
6	Input encrypted data buffer ptr
7	(outputbufsize<<4) | 12
8	Output cleartext data buffer ptr

Response

Index Word	Description
0	Header code
1	Result code

Description

This decrypts the input data with AES-CCM using keytype2, when the input noncesize is <12 the low 2-bits are cleared in the noncesize. The 12-byte nonce buffer used by NS is cleared to all-zero, then the nonce from inputbuf+0 with the noncesize is copied to this nonce buffer. NS then uses PS:EncryptSignDecryptVerifyAesCcm with keytype2 and with the above nonce buffer, where the inputptr is inputbuf+noncesize, outputptr is outputbuf+0, and size is inputbuffersize - noncesize - 16.

After decryption, NS copies the data at outbuf+blocksize to outbuf+blocksize+noncesize, with size inputbuffersize-blocksize-16. NS then copies the nonce from inputbuf+0 with the noncesize, to outbuf+blocksize.