How Mexico's Encrypted Code Safeguarded National Security

Since the emergence of the Federal Directorate of Security (DFS) in 1947, an encrypted language was established that allowed encrypted messages to be transmitted due to the level of information they handled considered national security and their functioning as political police. In this way, if the messages were intercepted or read by someone else outside the institution, they would not be able to understand it and, therefore, they would not discover the hidden communication.

The instruction of the coded language and the key words to be used was established directly by the presidency and entrusted to the Presidential General Staff. Because the DFS was attached to the executive branch during its first years, that is, directly to the presidency and, later, it became dependent on the Ministry of the Interior.

The Presidential General Staff internally presented a “Code instructions for the simple transposition system”[1] with the aim of helping to decipher the message. This communication was intended for the DFS, military and naval zones, garrisons, military attachés and state secretaries.

The cipher system was mainly based on numbering the code word according to its corresponding place in the alphabet. For example, if the keyword was MEXICO, the number 1 corresponded to the letter C, being encrypted as follows:

Another rule in the instructions corresponded to when the keyword had repeated letters. These letters would be numbered in successive order, from left to right:

There are several additional rules for encryption and decryption of longer messages. The interesting thing is that, since its founding, the DFS handled encrypted information. Beyond speculation or conspiracy theories, today, thanks to the AGN's documentary collection, we can be certain that this was the case. And it was known to other security institutions, such as the Presidential General Staff.

One of the rules that draws the most attention in the document is the one that refers to the destruction of the decrypted message, carried out on a sheet or document separate from the official one: “Do not do any decryption operation on the paper on which it is written.” the ciphertext. These operations must be done on separate paper and burned when the content is finished and known.”[2] This clearly exemplifies the high level of security that surrounded the information and the practice of leaving no trace of it.

The use of encrypted language by the DFS since its creation demonstrates the complex dynamics of security and confidentiality that characterized that historical period in Mexico. Beyond the controversies associated with DFS activities, this practice reveals the emphasis placed on safeguarding sensitive information in a political and social environment marked by uncertainty and tension. These

The use of encrypted language by the DFS since its creation demonstrates the complex dynamics of security and confidentiality that characterized that historical period in Mexico. Beyond the controversies associated with DFS activities, this practice reveals the emphasis placed on safeguarding sensitive information in a political and social environment marked by uncertainty and tension. These historical documents bear witness to an era when the protection of information was considered crucial.

Source: Archivo General de la Nación. “La Dirección Federal de Seguridad y el uso de lenguaje encriptado.” gob.mx, http://www.gob.mx/agn/es/articulos/la-direccion-federal-de-seguridad-y-el-uso-de-lenguaje-encriptado?idiom=es. Accessed 20 June 2024.