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Aug 09, 2020 Spark's 'Smart Inbox' sends messages that are important to you to the to,p and uses categories of Personal, Notifications, and Newsletters. Spark's scheduling feature allows you to assign a period during which it will send a particular message. Select from times later today, in the evening, tomorrow, or on any date. P7mViewer decodes smime.p7m files and other S/MIME messages.
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S/MIME (Secure/Multipurpose Internet Mail Extensions) is a standard for public keyencryption and signing of MIME data. S/MIME is on an IETFstandards track and defined in a number of documents, most importantly RFC3369, 3370, 3850 and 3851. It was originally developed by RSA Data Security and the original specification used the IETF MIME specification[1] with the de facto industry standard PKCS#7 secure message format. Change control to S/MIME has since been vested in the IETF and the specification is now layered on Cryptographic Message Syntax (CMS), an IETF specification that is identical in most respects with PKCS #7. S/MIME functionality is built into the majority of modern email software and interoperates between them. Since it is built on CMS, MIME can also hold an advanced electronic signature.
Function[edit]
S/MIME provides the following cryptographic security services for electronic messaging applications:
- Message integrity
- Non-repudiation of origin (using digital signatures)
- Privacy
- Data security (using encryption)
S/MIME specifies the MIME type
application/pkcs7-mime
[2] (smime-type 'enveloped-data') for data enveloping (encrypting) where the whole (prepared) MIME entity to be enveloped is encrypted and packed into an object which subsequently is inserted into an application/pkcs7-mime MIME entity.S/MIME certificates[edit]
Before S/MIME can be used in any of the above applications, one must obtain and install an individual key/certificate either from one's in-house certificate authority (CA) or from a public CA. The accepted best practice is to use separate private keys (and associated certificates) for signature and for encryption, as this permits escrow of the encryption key without compromise to the non-repudiation property of the signature key. Encryption requires having the destination party's certificate on store (which is typically automatic upon receiving a message from the party with a valid signing certificate). While it is technically possible to send a message encrypted (using the destination party certificate) without having one's own certificate to digitally sign, in practice, the S/MIME clients will require the user to install their own certificate before they allow encrypting to others. This is necessary so the message can be encrypted for both, recipient and sender, and a copy of the message can be kept (in the sent folder) and be readable for the sender.
A typical basic ('class 1') personal certificate verifies the owner's 'identity' only insofar as it declares that the sender is the owner of the 'From:' email address in the sense that the sender can receive email sent to that address, and so merely proves that an email received really did come from the 'From:' address given. It does not verify the person's name or business name. If a sender wishes to enable email recipients to verify the sender's identity in the sense that a received certificate name carries the sender's name or an organization's name, the sender needs to obtain a certificate ('class 2') from a CA who carries out a more in-depth identity verification process, and this involves making inquiries about the would-be certificate holder. For more detail on authentication, see digital signature.
Depending on the policy of the CA, the certificate and all its contents may be posted publicly for reference and verification. This makes the name and email address available for all to see and possibly search for. Other CAs only post serial numbers and revocation status, which does not include any of the personal information. The latter, at a minimum, is mandatory to uphold the integrity of the public key infrastructure.
Obstacles to deploying S/MIME in practice[edit]
- S/MIME is sometimes considered not properly suited for use via webmail clients. Though support can be hacked into a browser, some security practices require the private key to be kept accessible to the user but inaccessible from the webmail server, complicating the key advantage of webmail: providing ubiquitous accessibility. This issue is not fully specific to S/MIME: other secure methods of signing webmail may also require a browser to execute code to produce the signature; exceptions are PGP Desktop and versions of GnuPG, which will grab the data out of the webmail, sign it by means of a clipboard, and put the signed data back into the webmail page. Seen from the view of security this is a more secure solution.
- S/MIME is tailored for end-to-end security. Logically it is not possible to have a third party inspecting email for malware and also have secure end-to-end communications. Encryption will not only encrypt the messages, but also the malware. Thus if mail is not scanned for malware anywhere but at the end points, such as a company's gateway, encryption will defeat the detector and successfully deliver the malware. The only solution to this is to perform malware scanning on end user stations after decryption. Other solutions do not provide end-to-end trust as they require keys to be shared by a third party for the purpose of detecting malware. Examples of this type of compromise are:
- Solutions which store private keys on the gateway server so decryption can occur prior to the gateway malware scan. These unencrypted messages are then delivered to end users.
- Solutions which store private keys on malware scanners so that it can inspect messages content, the encrypted message is then relayed to its destination.
- Due to the requirement of a certificate for implementation, not all users can take advantage of S/MIME, as some may wish to encrypt a message, with a public/private key pair for example, without the involvement or administrative overhead of certificates.
Any message that an S/MIME email client stores encrypted cannot be decrypted if the applicable key pair's private key is unavailable or otherwise unusable (e.g., the certificate has been deleted or lost or the private key's password has been forgotten). However, an expired, revoked, or untrusted certificate will remain usable for cryptographic purposes. Indexing of encrypted messages' clear text may not be possible with all email clients. Neither of these potential dilemmas is specific to S/MIME but rather cipher text in general and do not apply to S/MIME messages that are only signed and not encrypted.
S/MIME signatures are usually 'detached signatures': the signature information is separate from the text being signed. The MIME type for this is multipart/signed with the second part having a MIME subtype of application/(x-)pkcs7-signature. Mailing list software is notorious for changing the textual part of a message and thereby invalidating the signature; however, this problem is not specific to S/MIME, and a digital signature only reveals that the signed content has been changed.
Security issues[edit]
On May 13, 2018, the Electronic Frontier Foundation (EFF) announced critical vulnerabilities in S/MIME, together with an obsolete form of PGP that is still used, in many email clients.[3] Dubbed EFAIL, this is a particularly critical hit to S/MIME that will require significant coordinated effort by many email client vendors to fix.[4]
See also[edit]
- DomainKeys Identified Mail for server-handled email message signing.
- EFAIL, a security issue in S/MIME
- GNU Privacy Guard (GPG)
- Pretty Good Privacy (PGP), especially 'MIME Security with OpenPGP' (RFC 3156).
References[edit]
- ^RFC 2045: Multipurpose Internet Mail Extensions (MIME). Part One was published in November 1996.
- ^Mission-critical Active Directory: Architecting a Secure and Scalable Infrastructure for Windows 2000. 2001. p. 550.
S/MIME adds new MIME content types that provide data confidentiality, integrity protection, nonrepudiation, and authentication services: application/pkcs7-mime, multipart/signed, and application/pkcs7-signature
- ^Gebhart, Danny O'Brien and Gennie (2018-05-13). 'Attention PGP Users: New Vulnerabilities Require You To Take Action Now'. Electronic Frontier Foundation. Retrieved 2018-05-29.
- ^Hansen, Robert (2018-05-20). 'Efail: A Postmortem'. Robert Hansen. Retrieved 2018-05-30.
External links[edit]
- RFC 5652: Cryptographic Message Syntax (CMS)
- RFC 3370: Cryptographic Message Syntax (CMS) Algorithms
- RFC 5751: Secure/Multipurpose Internet Mail Extensions (S/MIME) Version 3.2 Message Specification
- RFC 8551: Secure/Multipurpose Internet Mail Extensions (S/MIME) Version 4.0 Message Specification
- Microsoft Exchange Server: Understanding S/MIME (high-level overview).
Retrieved from 'https://en.wikipedia.org/w/index.php?title=S/MIME&oldid=975868871'
To send encrypted messages, you need the recipient's certificate (public key). Mail accesses this certificate using one of two methods, depending on whether the recipient is in your Exchange environment. This article explains both methods.
Message encryption
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When configuring S/MIME for your account, you can choose to 'Encrypt by Default' when composing new messages.
In iOS 13.4 and later, when you reply or forward a message, the encryption state of your message will match the state of the incoming message rather than your system default setting. You can also change the encryption state of an outgoing message using the blue lock icon:
Send encrypted messages to people in your Exchange environment
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If your recipient is a user in the same Exchange environment, iOS can find the necessary certificate for message encryption.
Follow these steps to send encrypted messages to contacts in your Exchange environment: Bosch mfi pump manual download.
- Compose a new message in Mail. Notice the unlocked lock icon, indicating that message encryption is enabled for your Exchange account.
- Begin addressing the message to a recipient in your Exchange organization.
- Mail consults the GAL to discover the recipient's S/MIME certificate.
- When Mail finds a certificate, a lock icon appears to the right of the recipient's contact name, and the address is highlighted in blue. Notice the larger blue lock icon—it can be used to toggle encryption for the message allowing you to easily compose both encrypted and an unencrypted messages.
- If you add a recipient and Mail can’t find the certificate, that address is highlighted in red and an unlocked icon appears to the right of the recipient's address. The message designation will now show unlocked and Unable to Encrypt.
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Send an encrypted message to someone outside your Exchange environment
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If the intended recipient is outside the sender's Exchange environment or if the sender isn't using an Exchange account, the recipient's certificate must be installed on the device. Use these steps.
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- In a signed message from your intended recipient, tap the sender's address. Invalid signatures have a red question mark to the right of the sender's address. Mail indicates valid signatures with a blue check mark to the right of the sender's address.
- If the sender's certificate was issued by an unknown certificate authority, you can manually install the certificate for this email address. Tap View Certificate.
- To install and trust the sender's signing certificate, tap Install.
- The Install button changes color to red and reads Remove. Tap Done in the upper-right to complete the certificate-installation process.
- iOS associates this digital certificate with the recipient's email address, allowing for message encryption.