CBC mode has the self-healing property: if one block of the cipher

is altered, the error propagates for at most two blocks. For example: let

the block size be 64 bits.

The original plaintext is

3231343336353837 3231343336353837 3231343336353837

The correct ciphertext is

ef7c4bb2b4ce6f3b f6266e3a97af0e2c 746ab9a6308f4256

If the ciphertext is corrupted, with the byte 0x4b changed to 0x4c:

ef7c4cb2b4ce6f3b f6266e3a97af0e2c 746ab9a6308f4256

Then it is decrypted to

efca61e19f4836f1 3231333336353837 3231343336353837

Explain the self-healing property using the decryption formulas.