Read And Decrypt Image" Button; Figure 13. "St25Dv-I2C Crypto Demo" - Data Transfer - ST ST25DV-I2C User Manual

2. The ST25DV-I2C-DISCO firmware reads the mailbox buffer and decrypts the command.
3. The ST25DV-I2C-DISCO firmware encrypts and writes the data through I2C to the ST25DV-I2C FTM
mailbox buffer.
4. The Android phone reads over NFC and decrypts the mailbox buffer content to finally display the
corresponding graph. The same graph is displayed on the ST25DV-I2C-DISCO board.
Note: The shape of the curve can be changed, simply by touching the plot on the ST25DV-I2C-DISCO screen. The
user then restarts the transfer to receive the new set of points.
3.2.4

"Read and decrypt image" button

Once the STC is ready, the user must click on "read and decrypt image" button to download a picture from the
ST25DV-I2C-DISCO.
The transfer occurs by following steps:
1. The Android smartphone writes an encrypted command to the ST25DV-I2C FTM mailbox buffer to request
an image.
2. The ST25DV-I2C-DISCO firmware reads the mailbox buffer and decrypts the command.
3. The ST25DV-I2C-DISCO firmware encrypts the picture and writes all the chunks of the picture through I2C
to the ST25DV-I2C FTM mailbox buffer.
4. The Android phone reads the chunks over NFC and decrypts the encrypted picture to finally display it.
The picture is also displayed on the ST25DV-I2C-DISCO board, along with the metrics of the transfer:
• Picture size, in bytes
• Transfer size, also considering the metadata, in bytes
• The total time, in milliseconds
• The time spent to encrypt the picture, in milliseconds
UM2575 - Rev 1
Figure 13. "ST25DV-I2C Crypto Demo" - data transfer
"ST25DV-I2C Crypto Demo" application screen
UM2575
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