Eleven Days to Expiry: TLS, Kiosks and Tape Keys
Fairhaven Mutual is a 380-employee credit union. Its member portal terminates TLS on a load balancer whose profile still offers TLS 1.0 and 1.1, RSA key exchange and CBC cipher suites, kept "for compatibility". Three branch self-service kiosks run Windows Embedded on hardware from a vendor that has exited the market; they cannot negotiate anything above TLS 1.0 with RSA. The portal also handles roughly 2,100 member logins a month.
The portal's private key and its passphrase sit in a configuration file readable by the web tier's service account, and the certificate expires in eleven days. No team has been assigned to renew it.
Separately, the nightly core-banking backup is written to LTO-8 tapes that leave the building in a courier van. The tapes are unencrypted, and the tape library shares a rack with the backup server. A regulator examination is scheduled for the following quarter, and the last budget cycle removed the hardware security module line item as "nice to have".
1. Rank the cryptographic remediation work and state what must be completed in the next eleven days and why.
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Eleven-day horizon - the certificate is the only item with a certain, dated impact. An expired certificate breaks the member portal for everyone: a guaranteed outage, guaranteed member-visible, guaranteed examiner-visible. Assign a named owner today, renew with adequate lead time, and inventory every other certificate in the estate with an expiry register and automated renewal so this does not recur. Certainty beats severity in the short window.
Close behind it: the private key material. A key and passphrase in a file readable by the web tier's service account means any web-tier compromise becomes a portal impersonation capability, and it also defeats the point of the certificate. Move the key into a hardware security module or, at minimum, a key management service with access restricted to a dedicated identity, and reissue the certificate with a new key rather than importing the exposed one. Rotation matters here: the current key must be treated as potentially disclosed.
Then the protocol profile - but only after the kiosks are addressed. Disable TLS 1.0/1.1, RSA key exchange and CBC suites, leaving TLS 1.2 and above with ephemeral key exchange and AEAD ciphers. RSA key exchange is the substantive flaw in that profile because it lacks forward secrecy: a later compromise of the server key decrypts previously captured sessions. CBC suites add padding-oracle exposure. TLS 1.0/1.1 are deprecated and increasingly rejected by clients and scanners anyway.
Do not confuse urgency with sequence. Renewing first, then re-keying, then tightening the profile means each step is independently reversible and none of them is done during an outage.
2. What do you do about the three kiosks that cannot move past TLS 1.0, and how do you justify the decision?
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The temptation is to hold the whole portal profile at TLS 1.0 so that three devices keep working. Quantify the trade: three kiosks versus roughly 2,100 member logins a month, plus every other member's browser, plus the examination finding. The tail should not wag the dog.
Options, in order of preference:
- Replace the kiosks. Cleanest, and the hardware is unsupported regardless of TLS - this is a refresh that is overdue on its own merits, not a security tax.
- Isolate and accept, with a date. If replacement cannot happen before the profile change, keep a separate legacy listener bound to a dedicated address and port, reachable only from the kiosk VLAN's source addresses, while the member-facing profile moves to TLS 1.2+ with AEAD ciphers. The kiosks get a bespoke endpoint, not a weakened main portal.
- Front the kiosks with a local proxy that terminates legacy TLS on the kiosk VLAN and re-originates modern TLS to the portal. Viable if the kiosk software permits a proxy configuration; verify rather than assume.
Whichever path is taken, the compensating controls are the same: kiosks on their own VLAN with egress restricted to the portal only, no general internet browsing, host-based lockdown so the device cannot be repurposed, and monitoring for anomalous requests from those source addresses.
Justification language for the risk owner: this is a documented, time-boxed risk acceptance covering three fixed-function devices on a controlled network, with a named owner, a compensating-control set, and an expiry date tied to the hardware refresh. A risk acceptance without an expiry date is a decision to keep the weakness forever. Present it to the examiner that way - examiners generally accept a reasoned, dated acceptance and reject an undocumented one.
3. The tape library and the backup server share a rack. Does encrypting the tapes actually reduce risk here, and what key management model would you propose?
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Encryption reduces risk only for the threats where the key is not travelling with the data. Be explicit about which threat you are buying down.
What it does protect against: a tape lost, stolen or misdelivered in transit or in storage. That is the realistic and recurrent loss event for offsite media, and drive-level encryption with keys held outside the tape handles it.
What it does not protect against: an attacker who reaches the backup server or the key store. If the key sits in the same rack, on the same domain, reachable from the same compromised account, then rack-level compromise yields both halves and the encryption is decorative. The shared rack is a finding in its own right - separate the tape library and the key material physically and logically, and remove the backup server's domain dependency where the platform allows it.
Proposed model:
- Encryption performed by the tape drive or library, with keys generated and wrapped by a key management service or HSM in a different administrative domain from the backup infrastructure.
- Key material never stored on the tapes, never in the backup catalogue, and not recoverable using only domain credentials held by the backup administrators.
- Split knowledge for the top-level key: two custodians required to export or restore it, with the procedure tested.
- Documented, tested restore including the key-recovery path. An encrypted backup nobody can restore is worse than no backup, because it looks like one.
- Rotation policy and a retention rule that keeps keys alive at least as long as the tapes they decrypt.
On the HSM that was cut from the budget: it now serves two requirements - the portal private key and the tape key wrapping - which changes the cost-benefit case materially. Reframe it as one control satisfying two examination findings rather than a standalone luxury.