chiffrer bedeutet auf Englisch

encrypt [encrypted, encrypting, encrypts]▼◼◼◼(to conceal information by means of a code or cipher)
verb
[UK: ɪn.ˈkrɪpt] [US: en.ˈkrɪpt]

Roman numeral▼◼◼◼(numeral represented by letters)
noun
[UK: ˈrəʊ.mən ˈnjuː.mə.rəl] [US: ˈroʊ.mən ˈnuː.mə.rəl]

decipher [deciphered, deciphering, deciphers]▼◼◼◼(to decode or decrypt a code or cipher)
verb
[UK: dɪ.ˈsaɪ.fə(r)] [US: də.ˈsaɪ.fər]His handwriting is impossible to decipher. = Il est impossible de déchiffrer son écriture.

decrypt [decrypted, decrypting, decrypts]▼◼◼◻(to convert back to plain text)
verb
[UK: diː.ˈkrɪpt] [US: diː.ˈkrɪpt]