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Last active February 4, 2018 00:22
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Let's Encrypt Cert and Key Security information
  • Why it's acceptable for Let's Encrypt's root to be sha-1 signed and why root certificates are exempt from SHA1 sunsetting: https://community.letsencrypt.org/t/sha-1-signed-certificate-in-chain/24897/2
  • Currently Let’s Encrypt only signs end-entity certificates with RSA intermediates. Let’s Encrypt will generate an ECDSA root and intermediates [in the future] which can be used to sign end-entity certificates [ref].
    • The benefit of an ECDSA authentication key (over RSA) is speed.
    • RSA don't scale very well as you increase bit size compared to ECDSA [ref: Section 1.1]
  • You should only support suites that use ECDHE and DHE as they offer Perfect Forward Secrecy. How to read a cipher suite [ref]:
    TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256
    ---------------------------------------
    TLS - the protocol used
    ECDHE - the key exchange mechanism
    ECDSA - the algorithm of the authentication key
    AES - the symmetric encryption algorithm
    128 - the key size of the above
    GCM - the mode of the above
    SHA256 - the MAC used by the algorithm
    
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