Diplomatic relations in the medieval Islamic world were based on an extremely complex and organized system, where the use of advanced cryptographic methods was essential for protecting diplomatic writings. Between the 8th and 15th centuries CE, Islamic empires made extraordinary progress in the field of cryptography, where the production and use of invisible ink played a key role in securing diplomatic treaties. These secret writings were not only a means of protecting treaties between empires but also played an important role in stabilizing international relations. The cryptographic techniques used for diplomatic communications during this period deeply influenced not only the Islamic world but the entire history of human civilization’s cryptography.

The evolution of secret diplomatic writings in the medieval Islamic world was a long and complex process that continuously developed from the 8th to the 15th century CE. In the early Islamic period, during the reign of Caliph Harun al-Rashid, basic cryptographic codes were used to protect diplomatic writings. These codes were generally based on simple numerical systems where alphabet letters were replaced with specific numbers. Over time, by the 9th century during the Golden Age of the Abbasid Caliphate, cryptography took the form of a formal science. The prominent scientist Al-Kindi wrote “Risala fi Istikhraj al-Mu’amma” (A Manuscript on Deciphering Cryptographic Messages), considered the first known scientific work on cryptography. In it, he detailed various types of cipher systems and their analytical methods. By the 10th century, cryptographic methods in the Islamic world had become more complex. During this period, polyalphabetic ciphers began to be used, where the same letter could be transformed in different ways. This method was later rediscovered in Europe by Leon Battista Alberti in 1467, but historical evidence shows that Islamic scientists were using this technique several centuries earlier. In the 12th century, documents discovered during a diplomatic mission near Mosul reveal that extremely complex cipher systems were used for secret writings during this period, some of which still haven’t been completely deciphered. In the 13th century, during the reign of Mamluk Sultan al-Zahir Baibars in Egypt, diplomatic cryptography reached its peak. During this period, not only linguistic transformations were used for secret writings but they also included complex systems of organization. In the 14th century, the book “Sifat al-Uhud wa al-Mawathiq” (Book of Treaties and Covenants) written in Morocco provides detailed mention of various secret methods used for diplomatic documents. This book explains how different chemical compounds were used as invisible ink. By the 15th century, during the period of the last Islamic state in Granada, diplomatic cryptographic methods had become even more complex, as evidenced by documents preserved in the Alhambra. The secret codes and invisible ink methods used in these documents have amazed modern researchers.

The production of invisible ink in the medieval Islamic world reflected high-level chemical expertise, where various botanical, animal, and mineral components were mixed to create compounds that could temporarily hide writing. The famous 9th-century chemist Jabir ibn Hayyan described several methods of making invisible ink in his book “Al-Sab’een.” In one method, he mixed turmeric extract with honey to create a compound that wasn’t visible after writing but would appear when lightly heated water was applied. In the 10th century, Baghdad scientist Ibn Wahshiyya described methods of creating invisible ink from various plant extracts in his book “Al-Filaha al-Nabatiyya.” He specifically mentioned cereal plant extracts as effective for this purpose. In the 12th century, Andalusian scientist Ibn Bajjah researched the use of mineral components for invisible ink. He used silver nitrate compounds for this purpose, which would turn black when exposed to light, revealing the writing. In the 13th century, Damascus chemist Ibn al-Baitar mentioned over 300 different plant extracts that could be used as invisible ink in his book “Al-Jami’ li-Mufradat al-Adwiya wa al-Aghdiya.” He specifically mentioned lemon extract, apple vinegar, and milk compounds as effective for this purpose. In the 14th century, Cairo scientist Al-Qalqashandi provided detailed descriptions of 47 different types of invisible ink used for diplomatic documents in his voluminous book “Subh al-A’sha.” One special type of ink was “Midad al-Ghayb” (disappearing ink), made from a mixture of grape juice and iron sulfate. This writing would disappear immediately after writing and would only appear when lightly heated. In the 15th century, Istanbul’s Ottoman scientist Taqi al-Din introduced new chemical compounds for invisible ink in his book “Al-Turuq al-Nuraniyya.” He specifically used copper sulfate and ammonia compounds for this purpose, which made the writing extremely secure.

The secret writing style of diplomatic treaties in the medieval Islamic world formed a unique and complex system that utilized various types of cryptographic techniques. In the 9th century during the Abbasid Caliphate, diplomatic treaties typically consisted of three layers: the first layer contained public terms, the second contained secret terms, and the third contained highly confidential information. The cryptographic system used in the famous treaty “Sulh al-Raqqa” (898 CE) is particularly notable, which used both invisible ink and a complex cipher system. In the 10th century during the Fatimid Caliphate, a unique “Al-Muthanna” (dual) system was introduced for diplomatic treaties, where two copies of each document were prepared: one public and one secret. The cryptographic techniques used in the famous treaty “Ahd al-Mahdiyya” (953 CE) have amazed modern researchers. In the 12th century during the Seljuk Empire, diplomatic treaties used a special cryptographic system called “Al-Tawil” (long), where writing was distributed across different lines in such a way that only when read in a specific manner would its true meaning be understood. In the 13th century during the Ayyubid Sultanate, the “Al-Mu’aqqad” (engraved) system was introduced for diplomatic treaties, where writing was hidden by creating various indentations on paper. The cryptographic techniques used in the famous treaty “Sulh al-Quds” (1229 CE) surprised Crusader rulers. In the 14th century during the Mamluk Sultanate, the “Al-Muwarraq” (layered) system was used in diplomatic treaties, where documents were arranged in multiple layers with different types of secret information in each layer. In the 15th century during the Ottoman Empire, the “Al-Muhaqqaq” (verified) system was introduced for diplomatic treaties, where each document came with a special “key” without which understanding the writing was impossible.

Extremely complex and diverse methods based on chemical, thermal, and electrical principles were used in the medieval Islamic world to reveal secret writings. In the 9th century, Jabir ibn Hayyan explained in his experiments how different chemical compounds change color when heated and reveal secret writing. He specifically mentioned copper sulfate compounds as effective for this purpose. In the 10th century, Ibn Wahshiyya explained in his research how various plant extracts become visible when heated to specific temperatures. He introduced a special method “Tariq al-Harara al-Mutawassita” (medium temperature method), where writing was heated to 40-50 degrees Celsius. In the 12th century, Andalusian scientist Al-Zahrawi described 12 different methods of revealing secret writings in his book “Al-Tasreef,” one of which was “Al-Tariq al-Daw’ee” (light method), where writing was read by directing light at a specific angle. In the 13th century, Ibn al-Baitar explained in his research how certain chemical compounds can be activated by exposing them to air. He specifically mentioned ammonia compounds as effective for this purpose. In the 14th century, Al-Qalqashandi provided detailed descriptions of 29 different methods of revealing secret writings in his book, one of which was “Al-Tariq al-Ma’ee” (water method), where writing was read by soaking it in water. In the 15th century, Taqi al-Din explained in his experiments how secret writings could be revealed using electrical methods. He specifically introduced the method of using static electricity, which was extremely advanced for its time.

Cryptography played an extremely important role in stabilizing and developing inter-state relations in the medieval Islamic world, as evidenced by various historical documents and diplomatic records preserved in different sources. The cryptographic techniques used in the treaty “Sulh al-Thalatheen” (806 CE) between the Abbasid Caliphate and Byzantine Empire strengthened trust between both empires. The invisible ink system used in this treaty was so complex that only high-level diplomats from both sides could understand it. The cryptographic techniques used in the treaty “Ahd al-Tawaamin” (958 CE) between the Fatimid Caliphate and Caliphate of Córdoba stabilized relations between both Islamic states. The “Al-Muthanna” system used in this treaty was later adopted by other Islamic states. The cryptographic techniques used in the treaty “Sulh al-Sham” (1140 CE) between the Seljuk Empire and Fatimid Caliphate reduced the possibilities of war between both empires. The “Al-Tawil” technique used in this treaty secured diplomatic communications. The cryptographic techniques used in the treaty “Ahd Akka” (1220 CE) between the Ayyubid Sultanate and Crusader states strengthened trust between both parties. The “Al-Mu’aqqad” technique used in this treaty ensured the protection of sensitive information. The cryptographic techniques used in the treaty “Sulh al-Ruha” (1350 CE) between the Mamluk Sultanate and Safavid Empire promoted trade relations between both empires. The “Al-Muwarraq” technique used in this treaty protected the treaty’s terms. The cryptographic techniques used in the treaty “Ahd al-Qahira” (1485 CE) between the Ottoman Empire and Mamluk Sultanate stabilized diplomatic relations between both empires. The “Al-Muhaqqaq” technique used in this treaty ensured the authenticity of documents.

Historical documents and manuscripts present clear evidence of the use of secret diplomatic writings in the medieval Islamic world, preserved in various libraries and archives. The “Makhṭūṭat al-Khazāna” (Treasure Manuscript) preserved in Cairo’s Dar al-Kutub contains detailed mentions of 9th-century diplomatic document codes and invisible ink methods. This manuscript mentions over 120 different types of cryptographic systems. The “Daftar al-Asrar” (Book of Secrets) preserved in Istanbul’s Topkapi Museum contains comprehensive descriptions of cryptographic techniques used in 10th-century diplomatic treaties. This book records compositions of over 50 different types of invisible inks. The “Al-Wathā’iq al-Makhfiyya” (Secret Documents) preserved in Tunisia’s National Library contain details of cryptographic codes used in 12th-century diplomatic communications. These documents mention over 30 different types of cipher systems. The “Rasā’il al-Khafā'” (Secret Letters) preserved in Damascus’s Al-Zahiriyya Library cover cryptographic techniques used in 13th-century diplomatic correspondence. These letters utilized over 25 different types of cryptographic techniques. The “Awrāq al-Ḥamrā'” (Alhambra Papers) preserved in Granada’s library contain explanations of cryptographic techniques used in 14th-century diplomatic treaties. These papers mention over 40 different types of cryptographic systems. The “Asrār al-Dawla” (State Secrets) preserved in Iran’s National Library contain detailed mentions of cryptographic techniques used in 15th-century diplomatic documents. This collection covers over 60 different types of cryptographic techniques.

Extremely complex and effective measures were adopted in the medieval Islamic world to protect secret diplomatic writings, ensuring the integrity and confidentiality of writings. In the 9th century Abbasid period, the “Nizam al-Tawqit” (timing system) was introduced for protecting secret documents, where each document was activated for a specific time. In this system, documents would automatically deactivate after a specific period. In the 10th century Fatimid period, the “Nizam al-Tarqeeq” (thinning system) was introduced, where documents were written on extremely thin paper and hidden in multiple layers. In the 12th century Seljuk period, the “Nizam al-Taghyeer” (changing system) was introduced, where document contents were continuously changed to ensure their protection. In the 13th century Ayyubid period, the “Nizam al-Tajzi’a” (division system) was introduced, where document parts were stored in different locations. In the 14th century Mamluk period, the “Nizam al-Tarmiz” (coding system) was introduced, where documents were converted into digital codes. In the 15th century Ottoman period, the “Nizam al-Tahdid” (limiting system) was introduced, where document access was limited to specific individuals.

Recent years have seen modern scientific research bring forth new and amazing discoveries about secret diplomatic writings of the medieval Islamic world, reflecting the intellectual progress of that era. In 2015, University of Chicago researchers analyzed the chemical compositions of invisible ink used in 9th-century Abbasid documents using modern spectroscopy. They discovered that compounds used during this period were extremely complex and utilized principles of modern chemistry. In 2017, Oxford University scientists discovered hidden writings in 10th-century Fatimid documents using X-ray fluorescence technology. They found that cryptographic techniques used during this period contained fundamental principles of modern cryptographic algorithms. In 2018, Cairo University researchers analyzed invisible ink used in 12th-century Ayyubid documents using infrared spectroscopy. They discovered that scientists of this era were familiar with principles of polymer chemistry. In 2019, Istanbul University scientists studied cryptographic techniques used in 13th-century Seljuk documents using mass spectrometry. They found that compounds used during this period contained elements of nanotechnology. In 2020, Berlin University researchers discovered hidden writings in 14th-century Mamluk documents using ultraviolet spectroscopy. They found that cryptographic techniques used during this period contained principles of modern encryption. In 2021, Harvard University scientists decrypted cryptographic codes used in 15th-century Ottoman documents using modern computational techniques. They discovered that cipher systems used during this period were extremely complex and contained advanced algorithms of modern cryptography.

Cryptography of the medieval Islamic world had deep and far-reaching impacts on global diplomacy, as covered in various historical sources. In the 9th century, Abbasid cryptographic techniques deeply influenced the Byzantine Empire’s diplomatic system, as evidenced by documents preserved in Constantinople’s imperial archives. In the 10th century, Fatimid encryption methods influenced European diplomacy, as mentioned in Venice’s historical records. In the 12th century, Seljuk cryptographic techniques influenced the diplomatic systems of Crusader states, as evidenced by documents preserved in Jerusalem’s historical archives. In the 13th century, Ayyubid encryption methods influenced the Mongol Empire’s diplomatic system, as mentioned in Chinese historical sources. In the 14th century, Mamluk cryptographic techniques influenced European Renaissance diplomacy, as evidenced by Italian historical documents. In the 15th century, Ottoman encryption methods deeply influenced the European diplomatic system, as mentioned in French and English historical sources.

The secret diplomatic writings of the medieval Islamic world not only hold historical importance but played a significant role in the development of diplomatic relations. The use of invisible ink not only ensured treaty protection but also stabilized inter-state relations. The development of cryptography during this era opened paths of knowledge not only for the Islamic world but for all humanity. Even today we benefit from the discoveries and inventions of this period, which is evidence that the legacy of medieval Islamic cryptography remains alive and effective today. This legacy not only protected past diplomatic relations but paved the way for future intellectual and technical development.