A quick Google shows there is a good deal of prior published work on the idea of time stamping with hashes. The Wikipedia articles on the topic lists published

A quick Google shows there is a good deal of prior published work on the idea of time stamping with hashes. The Wikipedia articles on the topic lists published references as early as 1991 and notes that the general idea itself dates to 1660 when Robert Hooke of Hooke's law fame published an anagram in a newspaper to timestamp his discovery. http://en.wikipedia.org/wiki/Linked_timestamping http://en.wikipedia.org/wiki/Linked_timestamping http://en.wikipedia.org/wiki/Trusted_timestamping#History http://en.wikipedia.org/wiki/Trusted_timestamping#History On another note, is using a bank transaction as a means of publishing even a good idea? The banks I use only keep recent transactions available online, between 6 months to two years. So, you would have to print out your bank statement save it and present that as the proof which isn't particularly convincing. With a newspaper anyone can go find a copy of that newspaper at a library and independently verify it. They won't be able to get your private bank records w/o a lot of hassle.