80-544: Ralph C. Merkle (born February 2, 1952) is an American computer scientist and mathematician. He is one of the inventors of public-key cryptography , the inventor of cryptographic hashing , and more recently a researcher and speaker on cryonics . Merkle is a renowned cryptographer, known for devising Merkle's Puzzles , co-inventing the Merkle–Hellman knapsack cryptosystem, and inventing cryptographic hashing ( Merkle–Damgård construction ) and Merkle trees . He has worked as
160-541: A chemical fixation step, sacrificing some structural preservation quality for less damage at the molecular level. Some scientists, like João Pedro Magalhães, have questioned whether using a deadly chemical for fixation eliminates the possibility of biological revival, making chemical fixation unsuitable for cryonics. Outside of cryonics firms and cryonics-linked interest groups, many scientists are very skeptical about cryonics methods. Cryobiologist Dayong Gao has said, "we simply don't know if [subjects have] been damaged to
240-469: A symmetric key , which is then used by symmetric-key cryptography to transmit data using the now-shared symmetric key for a symmetric key encryption algorithm. PGP , SSH , and the SSL/TLS family of schemes use this procedure; they are thus called hybrid cryptosystems . The initial asymmetric cryptography-based key exchange to share a server-generated symmetric key from the server to client has
320-639: A " brute-force key search attack ". However, such an attack is impractical if the amount of computation needed to succeed – termed the "work factor" by Claude Shannon – is out of reach of all potential attackers. In many cases, the work factor can be increased by simply choosing a longer key. But other algorithms may inherently have much lower work factors, making resistance to a brute-force attack (e.g., from longer keys) irrelevant. Some special and specific algorithms have been developed to aid in attacking some public key encryption algorithms; both RSA and ElGamal encryption have known attacks that are much faster than
400-411: A " man-in-the-middle attack " is possible, making any subordinate certificate wholly insecure. Most of the available public-key encryption software does not conceal metadata in the message header, which might include the identities of the sender and recipient, the sending date, subject field, and the software they use etc. Rather, only the body of the message is concealed and can only be decrypted with
480-437: A 61-year-old female writer of children's literature, became the first known Chinese national to have her head cryopreserved. Cryonics is generally regarded as a fringe pseudoscience. The Society for Cryobiology rejected members who practiced cryonics, and issued a public statement saying that cryonics is "not science". Russian company KrioRus is the first non-U.S. vendor of cryonics services. Yevgeny Alexandrov, chair of
560-629: A British cryptographer at the UK Government Communications Headquarters (GCHQ), conceived of the possibility of "non-secret encryption", (now called public key cryptography), but could see no way to implement it. In 1973, his colleague Clifford Cocks implemented what has become known as the RSA encryption algorithm , giving a practical method of "non-secret encryption", and in 1974 another GCHQ mathematician and cryptographer, Malcolm J. Williamson , developed what
640-407: A document or communication. Further applications built on this foundation include: digital cash , password-authenticated key agreement , time-stamping services and non-repudiation protocols. Because asymmetric key algorithms are nearly always much more computationally intensive than symmetric ones, it is common to use a public/private asymmetric key-exchange algorithm to encrypt and exchange
720-509: A frozen state is not considered possible now. Large vitrified organs tend to develop fractures during cooling, a problem worsened by the large tissue masses and very low temperatures of cryonics. Without cryoprotectants, cell shrinkage and high salt concentrations during freezing usually prevent frozen cells from functioning again after thawing. Ice crystals can also disrupt connections between cells that are necessary for organs to function. Some cryonics organizations use vitrification without
800-427: A historical writer. Merkle is married to Carol Shaw , the video game designer best known for the 1982 Atari 2600 game River Raid . Merkle is on the board of directors of the cryonics organization Alcor Life Extension Foundation . Merkle appears in the science fiction novel The Diamond Age , involving nanotechnology. Public-key cryptography Public-key cryptography , or asymmetric cryptography ,
880-414: A key length, the chief security risk is that the private key of a pair becomes known. All security of messages, authentication, etc., will then be lost. Additionally, with the advent of quantum computing , many asymmetric key algorithms are considered vulnerable to attacks, and new quantum-resistant schemes are being developed to overcome the problem. All public key schemes are in theory susceptible to
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#1732779659932960-691: A long list of "self-signed identity certificates" from PKI providers – these are used to check the bona fides of the certificate authority and then, in a second step, the certificates of potential communicators. An attacker who could subvert one of those certificate authorities into issuing a certificate for a bogus public key could then mount a "man-in-the-middle" attack as easily as if the certificate scheme were not used at all. An attacker who penetrates an authority's servers and obtains its store of certificates and keys (public and private) would be able to spoof, masquerade, decrypt, and forge transactions without limit, assuming that they were able to place themselves in
1040-604: A major advantage over your opponent. Only at the end of the evolution from Berners-Lee designing an open internet architecture for CERN , its adaptation and adoption for the Arpanet ... did public key cryptography realise its full potential. — Ralph Benjamin These discoveries were not publicly acknowledged for 27 years, until the research was declassified by the British government in 1997. In 1976, an asymmetric key cryptosystem
1120-550: A man-in-the-middle attack relatively straightforward. Capturing the public key would only require searching for the key as it gets sent through the ISP's communications hardware; in properly implemented asymmetric key schemes, this is not a significant risk. In some advanced man-in-the-middle attacks, one side of the communication will see the original data while the other will receive a malicious variant. Asymmetric man-in-the-middle attacks can prevent users from realizing their connection
1200-551: A manager at Elxsi , research scientist at Xerox PARC (Palo Alto Research Center), and a nanotechnology theorist at Zyvex . Merkle has held positions as a Distinguished Professor at Georgia Tech , senior research fellow at IMM, faculty member at Singularity University , and board member at Alcor Life Extension Foundation . He received the IEEE Richard W. Hamming Medal in 2010 and has published works on molecular manipulation and self-replicating machines . Ralph Merkle
1280-597: A prior shared secret. Merkle's "public key-agreement technique" became known as Merkle's Puzzles , and was invented in 1974 and only published in 1978. This makes asymmetric encryption a rather new field in cryptography although cryptography itself dates back more than 2,000 years. In 1977, a generalization of Cocks's scheme was independently invented by Ron Rivest , Adi Shamir and Leonard Adleman , all then at MIT . The latter authors published their work in 1978 in Martin Gardner 's Scientific American column, and
1360-493: A public key encryption system is for encrypting communication to provide confidentiality – a message that a sender encrypts using the recipient's public key, which can be decrypted only by the recipient's paired private key. Another application in public key cryptography is the digital signature . Digital signature schemes can be used for sender authentication . Non-repudiation systems use digital signatures to ensure that one party cannot successfully dispute its authorship of
1440-484: A purpose-built program running on a server computer – vouches for the identities assigned to specific private keys by producing a digital certificate. Public key digital certificates are typically valid for several years at a time, so the associated private keys must be held securely over that time. When a private key used for certificate creation higher in the PKI server hierarchy is compromised, or accidentally disclosed, then
1520-410: A suitable subject for scientific research, but marketing an unproven method to the public is quackery". According to cryonicist Aschwin de Wolf and others, cryonics can often produce intense hostility from spouses who are not cryonicists. James Hughes, the executive director of the pro-life-extension Institute for Ethics and Emerging Technologies , has not personally signed up for cryonics, calling it
1600-486: A trusted courier. This key, which both parties must then keep absolutely secret, could then be used to exchange encrypted messages. A number of significant practical difficulties arise with this approach to distributing keys . In his 1874 book The Principles of Science , William Stanley Jevons wrote: Can the reader say what two numbers multiplied together will produce the number 8616460799 ? I think it unlikely that anyone but myself will ever know. Here he described
1680-485: A wired route inside the sender's own building. In summation, public keys are easier to alter when the communications hardware used by a sender is controlled by an attacker. One approach to prevent such attacks involves the use of a public key infrastructure (PKI); a set of roles, policies, and procedures needed to create, manage, distribute, use, store and revoke digital certificates and manage public-key encryption. However, this has potential weaknesses. For example,
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#17327796599321760-560: A worthy experiment but saying, "I value my relationship with my wife." Cryobiologist Dayong Gao has said, "People can always have hope that things will change in the future, but there is no scientific foundation supporting cryonics at this time." While it is universally agreed that personal identity is uninterrupted when brain activity temporarily ceases during incidents of accidental drowning (where people have been restored to normal functioning after being completely submerged in cold water for up to 66 minutes), one argument against cryonics
1840-618: Is Tomorrow Biostasis GmbH, a Berlin -based firm offering cryonics and standby and transportation services in Europe . Founded in 2019 by Emil Kendziorra and Fernando Azevedo Pinheiro, it partners with the European Biostasis Foundation in Switzerland for long-term corpse storage. The facility was completed in 2022. It seems extremely unlikely that any cryonics company could exist long enough to take advantage of
1920-430: Is a grandnephew of baseball star Fred Merkle and is married to video game designer Carol Shaw . He serves on the board of directors of the cryonics organization Alcor Life Extension Foundation and appears in the science fiction novel The Diamond Age . While an undergraduate, Merkle devised Merkle's Puzzles , a scheme for communication over an insecure channel , as part of a class project at UC Berkeley. The scheme
2000-477: Is an abjectly false hope that is beyond the promise of technology and is certainly impossible with the frozen, dead tissue offered by the 'cryonics' industry". Anthropologist Simon Dein writes that cryonics is a typical pseudoscience because of its lack of falsifiability and testability. In his view, cryonics is not science, but religion: it places faith in nonexistent technology and promises to overcome death. William T. Jarvis has written, "Cryonics might be
2080-413: Is compromised. This remains so even when one user's data is known to be compromised because the data appears fine to the other user. This can lead to confusing disagreements between users such as "it must be on your end!" when neither user is at fault. Hence, man-in-the-middle attacks are only fully preventable when the communications infrastructure is physically controlled by one or both parties; such as via
2160-401: Is genuine by verifying the signature using the public key. As long as the software publisher keeps the private key secret, even if a forger can distribute malicious updates to computers, they cannot convince the computers that any malicious updates are genuine. For example, a journalist can publish the public key of an encryption key pair on a web site so that sources can send secret messages to
2240-532: Is legal in Germany for an indefinite period. Writing in Bioethics in 2009, David Shaw examined cryonics. The arguments he cited against it included changing the concept of death, the expense of preservation and revival, lack of scientific advancement to permit revival, temptation to use premature euthanasia, and failure due to catastrophe. Arguments in favor of cryonics include the potential benefit to society,
2320-399: Is medically alive. In France, cryonics is not considered a legal mode of body disposal; only burial, cremation, and formal donation to science are allowed, though bodies may legally be shipped to other countries for cryonic freezing. As of 2015, British Columbia prohibits the sale of arrangements for cryonic body preservation. In Russia, cryonics falls outside both the medical industry and
2400-454: Is never trivial and very rapidly becomes unmanageable as the number of participants increases, or when secure channels are not available, or when, (as is sensible cryptographic practice), keys are frequently changed. In particular, if messages are meant to be secure from other users, a separate key is required for each possible pair of users. By contrast, in a public-key cryptosystem, the public keys can be disseminated widely and openly, and only
2480-462: Is now known as Diffie–Hellman key exchange . The scheme was also passed to the US's National Security Agency . Both organisations had a military focus and only limited computing power was available in any case; the potential of public key cryptography remained unrealised by either organization: I judged it most important for military use ... if you can share your key rapidly and electronically, you have
Ralph Merkle - Misplaced Pages Continue
2560-501: Is now recognized to be an early example of public key cryptography . He co-invented the Merkle–Hellman knapsack cryptosystem , invented cryptographic hashing (now called the Merkle–Damgård construction based on a pair of articles published 10 years later that established the security of the scheme), and invented Merkle trees . The Merkle–Damgård construction is at the heart of many hashing algorithms. At Xerox PARC Merkle designed
2640-420: Is that a centuries-long absence from life might interrupt personal identity, such that the revived person would "not be themself". Maastricht University bioethicist David Shaw raises the argument that there would be no point in being revived in the far future if one's friends and families are dead, leaving them all alone, but he notes that family and friends can also be frozen, that there is "nothing to prevent
2720-411: Is the low-temperature freezing (usually at −196 °C or −320.8 °F or 77.1 K) and storage of human remains in the hope that resurrection may be possible in the future. Cryonics is regarded with skepticism by the mainstream scientific community. It is generally viewed as a pseudoscience , and its practice has been characterized as quackery . Cryonics procedures can begin only after
2800-778: Is the field of cryptographic systems that use pairs of related keys. Each key pair consists of a public key and a corresponding private key . Key pairs are generated with cryptographic algorithms based on mathematical problems termed one-way functions . Security of public-key cryptography depends on keeping the private key secret; the public key can be openly distributed without compromising security. There are many kinds of public-key cryptosystems, with different security goals, including digital signature , Diffie-Hellman key exchange , public-key key encapsulation , and public-key encryption . Public key algorithms are fundamental security primitives in modern cryptosystems , including applications and protocols that offer assurance of
2880-571: The Cryonics Institute ; his corpse was cryopreserved in 2011. In 1981, Robert Nelson, "a former TV repairman with no scientific background" who led the Cryonics Society of California, was sued for allowing nine bodies to thaw and decompose in the 1970s; in his defense, he claimed that the Cryonics Society had run out of money. This lowered the reputation of cryonics in the U.S. In 2018, a Y-Combinator startup called Nectome
2960-607: The Khufu and Khafre block ciphers and the Snefru hash function. Merkle was the manager of compiler development at Elxsi from 1980. In 1988, he became a research scientist at Xerox PARC . In 1999 he became a nanotechnology theorist for Zyvex . In 2003 he became a Distinguished Professor at Georgia Tech , where he led the Georgia Tech Information Security Center . In 2006 he returned to
3040-601: The Russian Academy of Sciences commission against pseudoscience, said there was "no scientific basis" for cryonics, and that the company was based on "unfounded speculation". Scientists have expressed skepticism about cryonics in media sources, and the Norwegian philosopher Ole Martin Moen has written that the topic receives a "minuscule" amount of attention in academia. While some neuroscientists contend that all
3120-510: The United States , and 1,500 people had made arrangements for cryopreservation of their remains. Economic considerations make it difficult for cryonics corporations to remain in business long enough to take advantage of any long-term benefits. The "patients", being dead, cannot continue to pay for their own preservation. Early attempts at cryonic preservation were made in the 1960s and early 1970s; most relied on family members to pay for
3200-446: The "patients" are clinically and legally dead . Procedures may begin within minutes of death, and use cryoprotectants to try to prevent ice formation during cryopreservation. It is not possible to reanimate a corpse that has undergone vitrification , as that damages the brain, including its neural circuits . The first corpse to be frozen was that of James Bedford , in 1967. As of 2014, about 250 bodies had been cryopreserved in
3280-421: The PKI system (software, hardware, and management) is trust-able by all involved. A " web of trust " decentralizes authentication by using individual endorsements of links between a user and the public key belonging to that user. PGP uses this approach, in addition to lookup in the domain name system (DNS). The DKIM system for digitally signing emails also uses this approach. The most obvious application of
Ralph Merkle - Misplaced Pages Continue
3360-751: The San Francisco Bay Area, where he has been a senior research fellow at IMM, a faculty member at Singularity University , and a board member of the Alcor Life Extension Foundation . He was awarded the IEEE Richard W. Hamming Medal in 2010. He is active in the field of molecular manipulation and self-replicating machines and has published books on the subject. Ralph Merkle is a grandnephew of baseball star Fred Merkle ; son of Theodore Charles Merkle, director of Project Pluto ; and brother of Judith Merkle Riley ,
3440-517: The advantage of not requiring that a symmetric key be pre-shared manually, such as on printed paper or discs transported by a courier, while providing the higher data throughput of symmetric key cryptography over asymmetric key cryptography for the remainder of the shared connection. As with all security-related systems, there are various potential weaknesses in public-key cryptography. Aside from poor choice of an asymmetric key algorithm (there are few that are widely regarded as satisfactory) or too short
3520-411: The algorithm came to be known as RSA , from their initials. RSA uses exponentiation modulo a product of two very large primes , to encrypt and decrypt, performing both public key encryption and public key digital signatures. Its security is connected to the extreme difficulty of factoring large integers , a problem for which there is no known efficient general technique. A description of the algorithm
3600-413: The attacker using the correct public keys for the different communication segments so as to avoid suspicion. A communication is said to be insecure where data is transmitted in a manner that allows for interception (also called " sniffing "). These terms refer to reading the sender's private data in its entirety. A communication is particularly unsafe when interceptions can not be prevented or monitored by
3680-434: The available metadata to a third party. The concept is based around an open repository containing separately encrypted metadata blocks and encrypted messages. Only the intended recipient is able to decrypt the metadata block, and having done so they can identify and download their messages and decrypt them. Such a messaging system is at present in an experimental phase and not yet deployed. Scaling this method would reveal to
3760-447: The brute-force approach. None of these are sufficiently improved to be actually practical, however. Major weaknesses have been found for several formerly promising asymmetric key algorithms. The "knapsack packing" algorithm was found to be insecure after the development of a new attack. As with all cryptographic functions, public-key implementations may be vulnerable to side-channel attacks that exploit information leakage to simplify
3840-515: The cause of death. In many cases, extensive tissue regeneration would be necessary. This revival technology remains speculative. Historically, people had little control over how their bodies were treated after death, as religion held jurisdiction over the matter. But secular courts began to exercise jurisdiction over corpses and use discretion in carrying out deceased people's wishes. Most countries legally treat preserved bodies as deceased persons because of laws that forbid vitrifying someone who
3920-441: The certificate authority issuing the certificate must be trusted by all participating parties to have properly checked the identity of the key-holder, to have ensured the correctness of the public key when it issues a certificate, to be secure from computer piracy, and to have made arrangements with all participants to check all their certificates before protected communications can begin. Web browsers , for instance, are supplied with
4000-495: The communication stream. Despite its theoretical and potential problems, Public key infrastructure is widely used. Examples include TLS and its predecessor SSL , which are commonly used to provide security for web browser transactions (for example, most websites utilize TLS for HTTPS ). Aside from the resistance to attack of a particular key pair, the security of the certification hierarchy must be considered when deploying public key systems. Some certificate authority – usually
4080-415: The confidentiality and authenticity of electronic communications and data storage. They underpin numerous Internet standards, such as Transport Layer Security (TLS) , SSH , S/MIME , and PGP . Compared to symmetric cryptography , public-key cryptography can be too slow for many purposes, so these protocols often combine symmetric cryptography with public-key cryptography in hybrid cryptosystems . Before
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#17327796599324160-436: The corresponding private keys need be kept secret. The two best-known types of public key cryptography are digital signature and public-key encryption : For example, a software publisher can create a signature key pair and include the public key in software installed on computers. Later, the publisher can distribute an update to the software signed using the private key, and any computer receiving an update can confirm it
4240-405: The dead back to life and treat the diseases that killed them. Mind uploading has also been proposed. Cryonics can be expensive. As of 2018 , the cost of preparing and storing corpses using cryonics ranged from US$ 28,000 to $ 200,000. At high concentrations, cryoprotectants can stop ice formation completely. Cooling and solidification without crystal formation is called vitrification . In
4320-586: The disposal of the girl's body, although the judge urged ministers to seek "proper regulation" for the future of cryonic preservation after the hospital raised concerns about the competence and professionalism of the team that conducted the preservation procedures. In Alcor Life Extension Foundation v. Richardson , the Iowa Court of Appeals ordered the disinterment of Richardson, who was buried against his wishes, for cryopreservation. A detailed legal examination by Jochen Taupitz concludes that cryonic storage
4400-477: The funeral services industry, making it easier than in the U.S. to get hospitals and morgues to release cryonics candidates. In 2016, the English High Court ruled in favor of a mother's right to seek cryopreservation of her terminally ill 14-year-old daughter, as the girl wanted, contrary to the father's wishes. The decision was made on the basis that the case represented a conventional dispute over
4480-424: The late 1990s, cryobiologists Gregory Fahy and Brian Wowk developed the first cryoprotectant solutions that could vitrify at very slow cooling rates while still allowing whole organ survival, for the purpose of banking transplantable organs. This has allowed animal brains to be vitrified, thawed, and examined for ice damage using light and electron microscopy . No ice crystal damage was found; cellular damage
4560-487: The mainstream consensus in saying that the brain does not have to be continuously active to survive or retain memory. Cryonicists controversially say that a human can survive even within an inactive, badly damaged brain, as long as the original encoding of memory and personality can be adequately inferred and reconstituted from what remains. Cryonics uses temperatures below −130 °C , called cryopreservation , in an attempt to preserve enough brain information to permit
4640-414: The mid-1970s, all cipher systems used symmetric key algorithms , in which the same cryptographic key is used with the underlying algorithm by both the sender and the recipient, who must both keep it secret. Of necessity, the key in every such system had to be exchanged between the communicating parties in some secure way prior to any use of the system – for instance, via a secure channel . This requirement
4720-461: The news organization in ciphertext. Only the journalist who knows the corresponding private key can decrypt the ciphertexts to obtain the sources' messages—an eavesdropper reading email on its way to the journalist cannot decrypt the ciphertexts. However, public-key encryption does not conceal metadata like what computer a source used to send a message, when they sent it, or how long it is. Public-key encryption on its own also does not tell
4800-536: The point where they've 'died' during vitrification because the subjects are now inside liquid nitrogen canisters." Based on experience with organ transplants, biochemist Ken Storey argues that "even if you only wanted to preserve the brain, it has dozens of different areas which would need to be cryopreserved using different protocols". Revival would require repairing damage from lack of oxygen, cryoprotectant toxicity, thermal stress (fracturing), and freezing in tissues that do not successfully vitrify, followed by reversing
4880-485: The preservation and ended in failure, with all but one of the companies going out of business and the corpses thawed and disposed of. The remaining organization, Alcor , uses a patient care trust to ensure that their preservations can be supported indefinitely. Cryonicists argue that as long as brain structure remains intact, there is no fundamental barrier, given our current understanding of physics, to recovering its information content. Cryonics proponents go further than
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#17327796599324960-411: The private key of the intended recipient. This means that a third party could construct quite a detailed model of participants in a communication network, along with the subjects being discussed, even if the message body itself is hidden. However, there has been a recent demonstration of messaging with encrypted headers, which obscures the identities of the sender and recipient, and significantly reduces
5040-470: The procedure. Some customers opt to have only their brain cryopreserved ("neuropreservation"), rather than their whole body. As of 2014, about 250 corpses have been cryogenically preserved in the U.S., and around 1,500 people have signed up to have their remains preserved. As of 2016, there are four facilities that retain cryopreserved bodies, three in the U.S. and one in Russia. A more recent development
5120-510: The prospect of immortality, and the benefits associated with avoiding death. Shaw explores the expense and the potential payoff, and applies an adapted version of Pascal's Wager to the question. In 2016, Charles Tandy wrote in support of cryonics, arguing that honoring someone's last wishes is seen as a benevolent duty in American and many other cultures. Cryopreservation was applied to human cells beginning in 1954 with frozen sperm, which
5200-576: The recipient anything about who sent a message —it just conceals the content of the message. One important issue is confidence/proof that a particular public key is authentic, i.e. that it is correct and belongs to the person or entity claimed, and has not been tampered with or replaced by some (perhaps malicious) third party. There are several possible approaches, including: A public key infrastructure (PKI), in which one or more third parties – known as certificate authorities – certify ownership of key pairs. TLS relies upon this. This implies that
5280-467: The relationship of one-way functions to cryptography, and went on to discuss specifically the factorization problem used to create a trapdoor function . In July 1996, mathematician Solomon W. Golomb said: "Jevons anticipated a key feature of the RSA Algorithm for public key cryptography, although he certainly did not invent the concept of public key cryptography." In 1970, James H. Ellis ,
5360-1146: The respondents were familiar with cryonics, and about half of those familiar with it had learned of it from films or television. The town of Nederland, Colorado , hosts an annual Frozen Dead Guy Days festival to commemorate a substandard attempt at cryopreservation . Corpses subjected to the cryonics process include those of baseball players Ted Williams and his son John Henry Williams (in 2002 and 2004, respectively), engineer and doctor L. Stephen Coles (in 2014), economist and entrepreneur Phil Salin , and software engineer Hal Finney (in 2014). People known to have arranged for cryonics upon death include PayPal founders Luke Nosek and Peter Thiel , Oxford transhumanists Nick Bostrom and Anders Sandberg , and transhumanist philosopher David Pearce . Larry King once arranged for cryonics but, according to Inside Edition , changed his mind. Sex offender and financier Jeffrey Epstein wanted to have his head and penis frozen after death. The corpses of some are mistakenly believed to have undergone cryonics. The urban legend that Walt Disney 's remains were cryopreserved
5440-486: The revival of the cryopreserved person. Cryopreservation is accomplished by freezing with or without cryoprotectant to reduce ice damage, or by vitrification to avoid ice damage. Even using the best methods, cryopreservation of whole bodies or brains is very damaging and irreversible with current technology. Cryonicists call the human remains packed into low-temperature vats "patients". They hope that some kind of presently nonexistent nanotechnology will be able to bring
5520-547: The search for a secret key. These are often independent of the algorithm being used. Research is underway to both discover, and to protect against, new attacks. Another potential security vulnerability in using asymmetric keys is the possibility of a "man-in-the-middle" attack , in which the communication of public keys is intercepted by a third party (the "man in the middle") and then modified to provide different public keys instead. Encrypted messages and responses must, in all instances, be intercepted, decrypted, and re-encrypted by
5600-514: The sender. A man-in-the-middle attack can be difficult to implement due to the complexities of modern security protocols. However, the task becomes simpler when a sender is using insecure media such as public networks, the Internet , or wireless communication. In these cases an attacker can compromise the communications infrastructure rather than the data itself. A hypothetical malicious staff member at an Internet service provider (ISP) might find
5680-498: The subtleties of a human mind are contained in its anatomical structure, few will comment directly on cryonics due to its speculative nature. People who intend to be frozen are often "looked at as a bunch of kooks". Cryobiologist Kenneth B. Storey said in 2004 that cryonics is impossible and will never be possible, as cryonics proponents are proposing to "overturn the laws of physics, chemistry, and molecular science". Neurobiologist Michael Hendricks has said, "Reanimation or simulation
5760-524: The supposed benefits offered; historically, even the most robust corporations have only a one-in-a-thousand chance of lasting 100 years. Many cryonics companies have failed; as of 2018 , all but one of the pre-1973 batch had gone out of business, and their stored corpses have been defrosted and disposed of. Medical laboratories have long used cryopreservation to maintain animal cells, human embryos, and even some organized tissues, for periods as long as three decades. But recovering large animals and organs from
5840-539: The thawed-out freezee from making new friends", and that a lonely existence may be preferable to none at all. Suspended animation is a popular subject in science fiction and fantasy settings. It is often the means by which a character is transported into the future. The characters Philip J. Fry in Futurama and Khan Noonien Singh in Star Trek exemplify this trope. A survey in Germany found that about half of
5920-407: The third party only the inbox server being used by the recipient and the timestamp of sending and receiving. The server could be shared by thousands of users, making social network modelling much more challenging. During the early history of cryptography , two parties would rely upon a key that they would exchange by means of a secure, but non-cryptographic, method such as a face-to-face meeting, or
6000-538: Was due to dehydration and toxicity of the cryoprotectant solutions. Costs can include payment for medical personnel to be on call for death, vitrification, transportation in dry ice to a preservation facility, and payment into a trust fund intended to cover indefinite storage in liquid nitrogen and future revival costs. As of 2011, U.S. cryopreservation costs can range from $ 28,000 to $ 200,000, and are often financed via life insurance. KrioRus , which stores bodies communally in large dewars , charges $ 12,000 to $ 36,000 for
6080-517: Was published by Whitfield Diffie and Martin Hellman who, influenced by Ralph Merkle 's work on public key distribution, disclosed a method of public key agreement. This method of key exchange, which uses exponentiation in a finite field , came to be known as Diffie–Hellman key exchange . This was the first published practical method for establishing a shared secret-key over an authenticated (but not confidential) communications channel without using
6160-868: Was published in the Mathematical Games column in the August 1977 issue of Scientific American . Since the 1970s, a large number and variety of encryption, digital signature, key agreement, and other techniques have been developed, including the Rabin cryptosystem , ElGamal encryption , DSA and ECC . Examples of well-regarded asymmetric key techniques for varied purposes include: Examples of asymmetric key algorithms not yet widely adopted include: Examples of notable – yet insecure – asymmetric key algorithms include: Examples of protocols using asymmetric key algorithms include: Cryonics Cryonics (from Greek : κρύος kryos , meaning "cold")
6240-628: Was recognized for developing a method of preserving brains with chemicals rather than by freezing. The method is fatal, performed as euthanasia under general anesthesia, but the hope is that future technology will allow the brain to be physically scanned into a computer simulation, neuron by neuron. According to The New York Times , cryonicists are predominantly non-religious white men, outnumbering women by about three to one. According to The Guardian , as of 2008, while most cryonicists used to be young, male, and "geeky", recent demographics have shifted slightly toward whole families. In 2015, Du Hong,
6320-438: Was soon thawed and buried by relatives. The first body to be cryopreserved and then frozen in hope of future revival was that of James Bedford . Alcor 's Mike Darwin says Bedford's body was cryopreserved around two hours after his death by cardiorespiratory arrest (secondary to metastasized kidney cancer) on January 12, 1967. Bedford's corpse is the only one frozen before 1974 still preserved today. In 1976, Ettinger founded
6400-465: Was thawed and used to inseminate three women. The freezing of humans was first scientifically proposed by Michigan professor Robert Ettinger in The Prospect of Immortality (1962). In 1966, the first human body was frozen—though it had been embalmed for two months—by being placed in liquid nitrogen and stored at just above freezing. The middle-aged woman from Los Angeles, whose name is unknown,
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