UM1759 datasheet(32/50 Pages) STMICROELECTRONICS

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Wireless M-Bus firmware APIs

UM1759

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DocID026279 Rev 1

4.1.4

AES128_ctr.c: functions description

The list of encryption layer (which is also part of application layer) routines is given below as

described in aes128_ctr.c.

Table 42. WM-Bus AES key schedule for decryption routine

Name

AES_keyschedule_dec

Parameters

u32* key: user key

u32* exp: expanded key

Description

This routine computes the expanded key (expkey) according to key for

AES128 decryption

Return type

None

Table 43. WM-Bus add counter routine

Name

add_counter

Parameters

u32 *ctr : counter address

Description

This routine increment counter by one upon encryption of each block

Return type

None

Table 44. WM-Bus bit-wise XOR routine

Name

bitwise_xor

Parameters

unsigned char *ina: input block a address

unsigned char *inb: input block b address

unsigned char *out : output block address

Description

This routine is for implementing XOR operation of blocks

Return type

None

Table 45. WM-Bus decrypts PDU routine

Name

decrypt_pdu

Parameters

u32 *exp_key : expended key address

unsigned char *cipher: input cipher data address

int len: length

unsigned char *plain: output plain data address

Description

This routine decrypts the incoming stream

Return type

None

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