Yes, the seed included in your EMOZ certificate PDF is strictly secret. It is a unique, randomly generated 32-byte password that allows you (or someone you trust) to decrypt the encrypted metadata stored on the blockchain.
By default, we recommend not sharing this seed with anyone, in order to keep your data private.
However, you can choose to share it with trusted individuals (such as a lawyer, collaborator, or institution) if you want them to independently verify your ownership of a file.
Keep in mind: even after decryption, your email address is not stored in plain text. EMOZ stores only the SHA-256 hash of your email, which means that even if someone has the seed, they would also need to know your email address to verify that the metadata belongs to you. They can do so by hashing your email themselves and comparing it with the value decrypted from the blockchain.
In summary: you control the seed. While we recommend keeping it private, you are free to share it if needed for independent verification.