Privacy, Secrecy, and Cryptography in the Early Modern Period

Cryptography has been a tool for secrecy for millennia. As a way of ensuring information confidentiality, cryptography served to maintain military, diplomatic, occult, and personal knowledge restricted to people with the decoding key – or those determined enough to crack the code.

Giambattista della Porta‘s De furtivis literarum notis (1563)

In the past (as today), cryptography was tied to different material components. From Egyptian carvings, Ancient Greek Scytales, and even alleged hidden tattoos, attempts to pass on information in a concealed way continuously depended on clever use of substances, mediums, and devices. One of the game-changing tools of early modern cryptography was the cipher disk.

The first appearance of the cipher disk in a descriptive text was in the work of the humanist Leon Battista Alberti (1404-1472). In his treatise De Cifris (1467), he described two concentric disks, divided into cells containing letters and numbers. The larger disk was used for the plaintext, while the inner ring was for the ciphertext. The use of the disk allowed a much more accessible polyalphabetic cipher, which became one of the most robust forms of encryption for centuries to come.

Opuscoli morali di Leon Batista Alberti gentil’huomo firentino

The use of encoding and decoding devices also implied that access to them needed to be restricted. This added layer of secrecy resulted in very interesting strategies of concealment. A great example is a ciphering machine used in the court of Henry II of France, which was disguised as a book.

Musée d’Écouen

These layers helped to ensure secrecy, which was fundamental for early modern strategic communication. However, do these efforts of secrecy correlate with a concern over privacy? After all, most of the subjects deemed worthy of such level of concealment dealt with very public matters, such as political arrangements and war efforts.

The philosopher Sissela Bok provides a useful distinction between secrecy and privacy. In her work Secrets: On the Ethics of Concealment and Revelation, Bok describes how secrecy and privacy are entangled, but not equivalent.

“Having defined secrecy as intentional concealment, I obviously cannot take it as identical with privacy. I shall define privacy as the condition of being protected from unwanted access by others—either physical access, personal information, or attention. Claims to privacy are claims to control access to what one takes—however grandiosely—to be one’s personal domain. Through such claims, and the counterclaims they often generate, people try to reinforce or expand this control.

Privacy and secrecy overlap whenever the efforts at such control rely on hiding. But privacy need not hide; and secrecy hides far more than what is private. A private garden need not be a secret garden; a private life is rarely a secret life. Conversely, secret diplomacy rarely concerns what is private, any more than do arrangements for a surprise party or for choosing prize winners.

Why then are privacy and secrecy so often equated? In part, this is so because privacy is such a central part of what secrecy protects that it can easily be seen as the whole. People claim privacy for differing amounts of what they are and do and own; if need be, they seek the added protection of secrecy. In each case, their purpose is to become less vulnerable, more in control.” Bok, Secrets (1989), p. 11.

The relationship between secrecy and privacy is crucial for our work at the Centre for Privacy Studies, as it is present in so many early modern sources. During the symposium Practices of Privacy: Knowledge in the Making, we explored how secrecy was a tool for privacy, but also discussed that the existence of secrets depended on a significant level of privacy to be secured. In early modern Europe, cryptography and secrecy also become entangled with contemporaneous philosophical and theological debates, so issues of religious confession and approaches to the natural world had a significant impact on how strategies and techniques of concealment developed. As such, the interplay between privacy, secrecy, and cryptography is crucial for understanding how privacy was created in particular environments.

On January 28, the seminar Historical Notions of Privacy in Latin America will address one of the main figures in the history of early modern cryptography: Johannes Trithemius. Professor Francisco de Paula de Souza Mendonça Júnior will present his work-in-progress on Trithemius’ Polygraphia. More information can be found on PRIVACY’s website: https://teol.ku.dk/privacy/events/events-2020/online-privacy-seminar-historical-notions-of-privacy-in-latin-america/