History of Cryptanalysis in Timeline

By Popular Timelines Editorial Team · Updated: March 31, 2026

Cryptanalysis is the study of analyzing information systems to uncover hidden aspects, often to bypass cryptographic security and access encrypted messages without knowing the key. It involves breaking cryptographic systems, aiming to decipher encrypted data even when the cryptographic key is unavailable. The primary goal is to understand and exploit vulnerabilities in cryptographic algorithms or their implementations to recover plaintext or keys.

1920: Coining of the word "cryptanalysis"

In 1920, the word "cryptanalysis" was coined by William Friedman, marking a relatively recent formalization of the term despite the existence of code-breaking methods for much longer.

1980: Factoring a 50-digit number

In 1980, factoring a difficult 50-digit number required 10 elementary computer operations.

1983: Don Coppersmith's Algorithm

In 1983, Don Coppersmith discovered a faster method for finding discrete logarithms in certain groups. This required cryptographers to use larger or different types of groups to maintain the security of the Diffie-Hellman key exchange scheme.

1984: Factoring a 75-digit number

By 1984, advances in factoring algorithms allowed a 75-digit number to be factored in 10 computer operations.

1998: Lars Knudsen's classification of attacks on block ciphers

In 1998, cryptographer Lars Knudsen classified various types of attacks on block ciphers, categorizing them based on the amount and quality of secret information discovered during cryptanalysis.

2005: RSA key size considerations

In 2005, numbers with several hundred digits were still considered too hard to factor, although methods were anticipated to continue improving, thus requiring key sizes to keep pace for RSA or other methods such as elliptic curve cryptography to be used.

2010: Brian Snow's assessment of Cryptography's progress

In 2010, former NSA technical director Brian Snow commented that both academic and government cryptographers were "moving very slowly forward in a mature field."