Why is CRC32 verification important when manipulating PNG file chunks for steganography?

Each PNG chunk includes a 4-byte CRC32 checksum computed from the chunk type code and data. When you modify a chunk to hide a payload (e.g., appending data to an ancillary chunk), you must recalculate and update the CRC32 value. Otherwise, image viewers and parsers that validate integrity may reject the file. The article demonstrates verifying CRC32 using a custom C program, ensuring that hidden data passes checksum checks and the image remains valid.