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RM0090: Reference manual - STMicroelectronics

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Cryptographic processor (CRYP) <strong>RM0090</strong><br />

Figure 211 and Figure 212 illustrate AES-CTR encryption and decryption, respectively.<br />

Figure 211. AES-CTR mode encryption<br />

AHB2 data write<br />

(before CRYP<br />

is enabled)<br />

128, 192<br />

or 256<br />

AEA, encrypt<br />

1. K: key; C: cipher text; I: input Block; o: output block; Ps: plain text before swapping (when decoding) or<br />

after swapping (when encoding); Cs: cipher text after swapping (when decoding) or before swapping (when<br />

encoding); P: plain text; IV: Initialization vectors.<br />

557/1416 Doc ID 018909 Rev 3<br />

+1<br />

K0...3<br />

(I + 1) is written<br />

back into IV<br />

at same time<br />

than C is pushed<br />

in OUT FIFO<br />

DATATYPE<br />

IV0...1(L/R)<br />

DATATYPE<br />

O, 128 bits<br />

IN FIFO<br />

plaintext P<br />

swapping<br />

I, 128 bits<br />

+<br />

P, 128 bits<br />

Cs, 128 bit<br />

swapping<br />

C, 128 bits<br />

OUT FIFO<br />

ciphertext C<br />

Ps, 128 bits<br />

ai16073b

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