How Does Cryptography Build Trust in a Digital World?

This blog explains how cryptography underpins trust in the digital world by securing data, verifying identities, and enabling private, reliable communication.

You unlock your phone with your fingerprint. You send a message to a friend halfway across the world, and it arrives in seconds, visible only to the two of you. You buy something online, confident that your credit card number won’t fall into the wrong hands. What powers all of this? Cryptography. In today’s hyperconnected world, we generate and share enormous amounts of personal data which include texts, emails, passwords, bank transactions, health records. And we do it with an expectation, not just of privacy, but of trust. We expect the message we sent to arrive unaltered. We expect the website we’re using to be legitimate. We expect our identities to be protected. Cryptography makes that possible (Stallings, 2017; Menezes, van Oorschot, & Vanstone, 1996). It is more than a tool for keeping secrets. It is the foundation for digital trust. It proves who you are, ensures that information hasn't been tampered with, and protects communication from being intercepted. Cryptography is the invisible infrastructure behind every “https://”, every encrypted chat, every secure login (Rescorla, 2001).

At its core, cryptography transforms readable data (plaintext) into scrambled, unreadable text (ciphertext) so that only someone with the correct key can unlock it. This idea has existed for thousands of years, but its role has evolved far beyond military codes and hidden messages (Kahn, 1996). Today, it underpins everything from secure apps and cloud storage to online banking and digital identity (Rivest, Shamir, & Adleman, 1978).

In this introductory blog, the first in a series on cryptography, we’ll explore how simple secret codes from the past became the sophisticated systems securing our digital lives. We’ll keep things simple, while highlighting key historical milestones and core ideas that will unfold in future posts. The goal of this series is to help you understand what cryptography is, why it matters, and how it quietly enables trust in the digital world.

So, what exactly is cryptography?

The word cryptography comes from the Greek for "hidden writing," and for much of history, that was its main purpose: turning messages into secret code to keep them safe from prying eyes (Singh, 1999). But cryptography has evolved far beyond just secrecy. Today, it plays a central role in protecting data, verifying identity, and enabling trust in the digital world. It secures both the content of communication and its credibility. Institutions like the U.S. National Institute of Standards and Technology define cryptography as the science of protecting and verifying information. Its goals include confidentiality, integrity, and authenticity; all essential for secure interactions online (NIST, 2020).

Put simply, cryptography gives us the tools to do more than hide data. It allows us to prove things about that data. For instance, digital signatures can show who sent a message and guarantee that it was not changed along the way. This is a key part of how trust is built across digital systems (Rivest et al., 1978).

To understand cryptography from the ground up, let’s take a quick look at how it began and how it has changed over time.

A Journey Through Cryptographic History: From Secrecy to Digital Trust

It begins in ancient Rome with the Caesar cipher, a basic form of letter substitution that offered rudimentary secrecy in military communication. While simple, it marked the start of using systematic methods to protect information (Kahn, 1996). Fast forward to the 9th century, where Arab scholar Al-Kindi introduced frequency analysis, a groundbreaking technique for deciphering coded messages. This was the birth of cryptanalysis, a field that has since become as important as encryption itself (Kahn, 1996).

The Renaissance brought further advancements with the invention of the Vigenère cipher. By using multiple alphabets and a keyword, it resisted attacks that worked on earlier ciphers. It was considered unbreakable for centuries, a testament to how much complexity could be achieved with relatively simple tools. However, by the 19th century, cryptanalysis had caught up. Charles Babbage and Friedrich Kasiski independently cracked the Vigenère cipher, revealing the constant cat-and-mouse game between code-makers and code-breakers (Singh, 1999). During the same era, ciphers like Playfair and Hill introduced mathematical ideas that hinted at the algorithms of the future (Stallings, 2017).

The 20th century marked a turning point. The Enigma machine, used by Nazi Germany during World War II, applied mechanical complexity to encryption. It was considered secure until Allied efforts at Bletchley Park, led by figures like Alan Turing, successfully broke it using early computers. This was the first large-scale demonstration of how cryptography and computing could intersect (Hodges, 2012).

Then came the real revolution. In the 1970s, cryptography moved from secret government labs to the public domain. Diffie and Hellman introduced public-key cryptography, solving the long-standing problem of secure key exchange (Diffie & Hellman, 1976). Shortly after, RSA made it practical to encrypt messages and verify digital signatures without needing a shared secret (Rivest et al., 1978). By the 1990s and early 2000s, cryptography became a daily necessity. SSL/TLS, the protocols behind HTTPS, brought encryption to the masses, securing everything from online banking to email (Rescorla, 2001).

In the 2010s and beyond, cryptography entered a new frontier, enabling decentralized trust. Technologies like blockchain and cryptocurrencies use cryptographic hashes and public-key signatures not just to protect data, but to build systems that don’t require central authority (Nakamoto, 2008). From smart contracts to NFTs, cryptography now plays a central role in redefining ownership, value, and verification in the digital age.

What's next?

Cryptography today has become essential to establishing trust in a world where people, systems, and data interact constantly across digital spaces. It helps prove who you are, ensures data has not been altered, and keeps communication and transactions secure even without a shared location or authority (Stallings, 2017; NIST, 2020).

One example is the use of zero-knowledge proofs, which allow someone to prove they know something without revealing the actual information. These systems are already being used in privacy-preserving cryptocurrencies, digital identity platforms, and secure voting (Ben-Sasson et al., 2014; Zyskind, Nathan, & Pentland, 2015). They show how cryptography can offer both privacy and proof at the same time. Another powerful application is digital signatures. These are used in everything from verifying software updates to enabling secure e-governance. When your device downloads a system update, it checks the signature to confirm that it came from a trusted source and was not altered (Rivest, Shamir, & Adleman, 1978; Rescorla, 2001). Countries like Estonia and India rely on digital signatures to run secure online services at a national scale (Vassil, 2015; Press Information Bureau, 2021).A third example is multi-party computation, a technique that lets multiple parties work together to approve an action without revealing their individual inputs. This method is now widely used in financial systems to protect cryptographic keys (Evans, Kolesnikov, & Rosulek, 2018). Institutions use it to make sure no single person or device can access critical information on its own, reducing the risk of internal breaches or theft. These cases show that modern cryptography is no longer just about secrecy. It is about verifiability, accountability, and resilience. It builds confidence into the systems we rely on every day, from banking and healthcare to communication and governance.

In the next article of this series, we will take a closer look at how these cryptographic tools actually work. We will explore the key functions behind today’s security infrastructure, including encryption, hashing, digital signatures, and secure key exchange.

References

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Diffie, W., & Hellman, M. (1976). New directions in cryptography. IEEE Transactions on Information Theory, 22(6), 644–654. https://doi.org/10.1109/TIT.1976.1055638

Evans, D., Kolesnikov, V., & Rosulek, M. (2018). A pragmatic introduction to secure multi-party computation. Foundations and Trends® in Privacy and Security, 2(2–3), 70–246. https://doi.org/10.1561/3300000019

Hodges, A. (2012). Alan Turing: The enigma. Princeton University Press.

Kahn, D. (1996). The codebreakers: The comprehensive history of secret communication from ancient times to the internet. Scribner.

Menezes, A. J., van Oorschot, P. C., & Vanstone, S. A. (1996). Handbook of applied cryptography. CRC Press. https://doi.org/10.1201/9781439821916

Nakamoto, S. (2008). Bitcoin: A peer-to-peer electronic cash system. https://bitcoin.org/bitcoin.pdf

National Institute of Standards and Technology. (2020). Glossary of key information security terms (NIST IR 7298 Rev. 3). https://csrc.nist.gov/publications/detail/nistir/7298/rev-3/final

Press Information Bureau, Government of India. (2021). Digital India programme: Achievements and initiatives. https://pib.gov.in/PressReleasePage.aspx?PRID=1704700

Rescorla, E. (2001). SSL and TLS: Designing and building secure systems. Addison-Wesley.

Rivest, R. L., Shamir, A., & Adleman, L. (1978). A method for obtaining digital signatures and public-key cryptosystems. Communications of the ACM, 21(2), 120–126. https://doi.org/10.1145/359340.359342

Singh, S. (1999). The code book: The science of secrecy from ancient Egypt to quantum cryptography. Doubleday.

Stallings, W. (2017). Cryptography and network security: Principles and practice (7th ed.). Pearson.

Vassil, K. (2015). Estonian e-Government ecosystem: Foundation, applications, outcomes. Background Paper for the World Development Report. https://openknowledge.worldbank.org/handle/10986/23632

Zyskind, G., Nathan, O., & Pentland, A. (2015). Decentralizing privacy: Using blockchain to protect personal data. 2015 IEEE Security and Privacy Workshops. https://doi.org/10.1109/SPW.2015.27