Original fictional bags. No program encoded, hashed, or encrypted a value for this card.

Worked bags
Bag postcard
Declared operation: standard Base64
Key: none
Job: write bytes in the public alphabet from the encodings lesson
Secrecy: no. Anyone who knows that public alphabet can reverse it.

Bag tag
Declared operation: a hash function with a fixed-length result
Key: none
Job: produce a digest of the bytes
Secrecy: no. A digest is not ciphertext.
Comparison limit: a digest supports a comparison when the reference digest comes from a source you trust. A digest from the same person who can change the file matches the changed file.

Bag envelope
Declared operation: encryption
Key: held by the recipient and not printed on this card
Job: change the note into ciphertext so someone without the key does not learn the note
This is not the one-byte XOR toy. That toy used a published key.

Activity bags
Bag E
Declared operation: standard Base64
Goal written on the bag: send the bytes through a text form
Key: none

Bag H
Declared operation: a hash function
Goal written on the bag: compare this digest with a digest from a trusted source
Key: none

Bag C
Declared operation: encryption
Goal written on the bag: keep the note secret
Key: held by the recipient and not printed

Check: bag E is encoding.