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October 18, 2021 Archives

Monday, October 18, 2021

CONTINUITY: 1915 Vintage Western Electric “Candlestick” Phone

The classic Western Electric #20B candlestick telephone was patented in 1904 and remained in production until the 1920s, when it was supplanted by desktop phones with the transmitter and receiver in one handset. The candlestick phone contained no ringer, and was connected to a separate “subscriber set” or ringer box containing the bells. Later models for automatic exchanges added a rotary dial in the base. Many candlestick phones remained in service, leased and maintained by telephone companies, until the 1940s and '50s. They are electrically compatible with today's wired telephone networks.

The earpiece that hung on the hook was called the “receiver”, and the phone was answered by picking it up. A remnant of this remains in the English language, with many people continuing to call the handset of modern telephones “the receiver”. In French, the handset is called «le combiné», indicating it contains both the microphone and receiver.

Posted at 13:55 Permalink

CONTINUITY: Fat Finger—More Than 12,000 Ethereum Lost to Typos

Unlike Bitcoin public addresses, which incorporate a 32 bit checksum, the original specification for Ethereum public addresses was simply strings of 40 hexadecimal digits, for example 0xc9b83ab54c84aac4445b56a63033db3d5b017764. If somebody attempts to send funds to such an address and accidentally mistypes or transposes even a single digit of the address, the funds will be sent to an address whose private key is unknown and which is computationally intractable to discover (there are 1640≈1048 possible Ethereum addresses) and thus lost forever. Obviously, it is a poor idea to type in such an address, and errors in optical scanning, text editors, and cut and paste mechanisms all pose risks of error.

In 2018, Johannes Pfeffer decided to estimate the quantity of Ether (the name for the currency of the Ethereum system) lost by having been sent to mistyped addresses. The methodology was clever and simple: search the blockchain for pairs of addresses, both of which had received funds, but which differed only by one character. An address of such a pair which had no outgoing transactions was almost certainly a typographical error entering the other, because the probability of two such similar addresses being generated from independent known private keys is comparable to that of guessing the private key from a public address. He reported the results in “Over 12,000 Ether Are Lost Forever Due to Typos”.

As of the date of his study, 2,674 typos were found, affecting 2,053 accounts, with total funds lost amounting to ETH 12,622, which at this writing has a value in excess of US$ 47 million (when he did his study, it was “only” US$ 8.84 million). All of these funds have gone to the great bit bucket in the sky, never to be seen again.

It's odd that Ethereum addresses weren't designed from the outset to incorporate a checksum, especially since International Bank Account Numbers (IBAN) and Bitcoin addresses which pre-date Ethereum both include checksums. The reasoning appears to have been that the hexadecimal addresses would not be directly used by humans, but rather encoded forms such as the IBAN-compatible ICAP or through a domain name like system such as now exists with the Ethereum Name Service. But, in fact, Ethereum wallets and individuals went ahead and used the hexadecimal addresses without checksums, and the consequences were predictable.

In 2016, this situation became sufficiently embarrassing that Ethereum Improvement Proposal EIP-55, “Mixed-case checksum address encoding” specified a checksum of sorts, in which a hash of the original address is encoded in hexadecimal digits between “A” and “F” by writing them in upper or lower case letters. This provides an average of 15 check bits per address, which reduces the probability of an error not being detected to 0.0247%, which is around fifty times better than the two digit IBAN checksum. Almost all Ethereum clients now express addresses in this form and check any submitted address which contains mixed case hexadecimal digits. For compatibility, however, un-checksummed addresses with uniform case hexadecimal digits continue to be accepted.

It would be interesting to repeat the typo analysis and see what effect the introduction and widespread use of checksummed addresses has had on the rate and magnitude of losses to typos.

Posted at 12:00 Permalink

CONTEXT: Magnetic Mysteries—The “Simple Magnetic Over-Unity Toy”

Ignoring potential energy is the source of much confusion and “inspiration” to designers of perpetual motion machines of the first kind. Simple experiments with magnets demonstrate how confusing and deceptive it can be when all energy flows are not accounted for. Fortunately, physicists, engineers, and patent examiners have learned to approach claims of “over unity” (something for nothing) with extreme scepticism. Now if we could just get the economists and politicians on board.

Posted at 11:32 Permalink

TRACKING WITH CLOSEUPS: A Monolithic Schmidt-Cassegrain Telescope

A Schmidt-Cassegrain telescope has multiple optical elements: a spherical primary mirror, a hyperbolic secondary mirror, a Schmidt corrector plate (aspheric lens), and sometimes a field flattener lens to create a planar image. Could you make all of these out of one solid piece of glass?

Posted at 11:19 Permalink