After the war, Luhn entered the textile field, which eventually led him to the United States, where he invented a thread-counting gauge (the Lunometer) still on the market.
[3] From the late 1920s to the early 1940s, during which time he obtained patents for a broad range of inventions, Luhn worked in textiles and as an independent engineering consultant.
His introduction to the field of documentation/information science came in 1947 when he was asked to work on a problem brought to IBM by James Perry and Malcolm Dyson that involved searching for chemical compounds recorded in coded form.
These techniques included full-text processing; hash codes; Key Word in Context indexing (see also Herbert Marvin Ohlman); auto-indexing; automatic abstracting and the concept of selective dissemination of information (SDI).
Today, hashing algorithms are essential for many applications such as textual tools, cloud services, data-intensive research and cryptography among numerous other uses.