If I sign something, I want to feel assured that the contents of what I signed will not change later.Īs we saw with my contract example above, physical signatures do not provide this benefit. With a digital signature, I cannot claim that I did not sign something while at the same time claiming that my private key is indeed private. With a physical signature, I could try to claim that the signature was forged by someone else. If I sign something, I cannot later claim that the signature didn’t come from me.
With a digital signature, I cannot impersonate someone else, because the Certificate Authority will not issue a certificate to me unless I am able to demonstrate that I really am who I say I am. Physical signatures afford this protection to a degree, but of course, forgeries are possible.ĭigital signatures are created using certificates issued by Certificate Authorities. If I sign something, others will know it was signed by me and not someone else, because my signature is uniquely mine and cannot be forged. Before we look into how that works, let’s review all of the benefits provided with digital signatures.ĭigital signatures can provide these three benefits: If a digitally signed contract is tampered with, the signature is automatically invalidated. The integrity of the contract had been compromised, and this is something that would not have been possible to do if I had signed the contract using a digital signature. Their “Official” copy of the contract with the end date removed:įigure 2 – Contract with the end date removed My copy of the contract with the end date specified in the “Terms of Agreement” section:įigure 1 – Original contract with end date. If we had stayed with them, and if I hadn’t kept a copy of the contract that I signed with them, they could have claimed that I signed a contract for much longer than one year. They had removed the contract expiration date on their “official” copy of the contract. As part of the back and forth with canceling the new contract, the new company sent me a copy of the contract that I signed, and I noticed a small difference between what they sent me and the copy that I had kept after signing it. Our current waste removal company found out we were not going to renew, so they called and offered better terms and explained that if we extend our contract with them, it would supersede the new contract which I signed. We eventually decided to go with one of the other waste management companies, and I signed a one-year contract with them.
Our condo association was stuck in one of these automatic renewals for a year, and as that extra contract year came to an end, we shopped around for a better deal. Buried in the fine print is an explanation that the contract will automatically renew at a rate specified by the waste management company (which ends up being much higher than the original rate), and that canceling the automatic renewal must be done within a short time window that ends a month before the original three-year contract expires (probably to increase the chance that this is overlooked by the homeowner). The customer agrees to the rate and signs the contract. Here’s one way how this is done: The contract is set up with a negotiated rate for three years. These contracts are frequently structured in a way that causes homeowners to overpay. In Chicago, the city handles waste removal (trash pickup) for buildings with four units or less, and larger properties are required to contract with a private waste management company. Let’s look at an example.īack in 2011, I lived in a Chicago condominium building which had six units. Digital signatures serve a similar function as physical signatures, but they also provide additional benefits which physical signatures do not. FileMaker 18 introduces two new cryptographic functions which can be used to generate and verify digital signatures:ĬryptGenerateSignature ( data algorithm privateRSAKey keyPassword )ĬryptVerifySignature ( data algorithm publicRSAKey signature )ĭigital signatures are a digital analog to good old-fashioned physical signatures which we’re all familiar with.
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