Corrected two more bullets

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Gary Moore
2021-11-11 20:13:57 -08:00
parent e0ab8e7007
commit 1661c8f2c8

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@ -58,9 +58,9 @@ Although CNG sounds like a mundane starting point, it illustrates some of the ad
The Platform Crypto Provider, introduced in the Windows 8 operating system, exposes the following special TPM properties, which software-only CNG providers cannot offer or cannot offer as effectively:
**Key protection**. The Platform Crypto Provider can create keys in the TPM with restrictions on their use. The operating system can load and use the keys in the TPM without copying the keys to system memory, where they are vulnerable to malware. The Platform Crypto Provider can also configure keys that a TPM protects so that they are not removable. If a TPM creates a key, the key is unique and resides only in that TPM. If the TPM imports a key, the Platform Crypto Provider can use the key in that TPM, but that TPM is not a source for making more copies of the key or enabling the use of copies elsewhere. In sharp contrast, software solutions that protect keys from copying are subject to reverse-engineering attacks, in which someone figures out how the solution stores keys or makes copies of keys while they are in memory during use.
- **Key protection**. The Platform Crypto Provider can create keys in the TPM with restrictions on their use. The operating system can load and use the keys in the TPM without copying the keys to system memory, where they are vulnerable to malware. The Platform Crypto Provider can also configure keys that a TPM protects so that they are not removable. If a TPM creates a key, the key is unique and resides only in that TPM. If the TPM imports a key, the Platform Crypto Provider can use the key in that TPM, but that TPM is not a source for making more copies of the key or enabling the use of copies elsewhere. In sharp contrast, software solutions that protect keys from copying are subject to reverse-engineering attacks, in which someone figures out how the solution stores keys or makes copies of keys while they are in memory during use.
**Dictionary attack protection**. Keys that a TPM protects can require an authorization value such as a PIN. With dictionary attack protection, the TPM can prevent attacks that attempt a large number of guesses to determine the PIN. After too many guesses, the TPM simply returns an error saying no more guesses are allowed for a period of time. Software solutions might provide similar features, but they cannot provide the same level of protection, especially if the system restarts, the system clock changes, or files on the hard disk that count failed guesses are rolled back. In addition, with dictionary attack protection, authorization values such as PINs can be shorter and easier to remember while still providing the same level of protection as more complex values when using software solutions.
- **Dictionary attack protection**. Keys that a TPM protects can require an authorization value such as a PIN. With dictionary attack protection, the TPM can prevent attacks that attempt a large number of guesses to determine the PIN. After too many guesses, the TPM simply returns an error saying no more guesses are allowed for a period of time. Software solutions might provide similar features, but they cannot provide the same level of protection, especially if the system restarts, the system clock changes, or files on the hard disk that count failed guesses are rolled back. In addition, with dictionary attack protection, authorization values such as PINs can be shorter and easier to remember while still providing the same level of protection as more complex values when using software solutions.
These TPM features give Platform Crypto Provider distinct advantages over software-based solutions. A practical way to see these benefits in action is when using certificates on a Windows device. On platforms that include a TPM, Windows can use the Platform Crypto Provider to provide certificate storage. Certificate templates can specify that a TPM use the Platform Crypto Provider to protect the key associated with a certificate. In mixed environments, where some computers might not have a TPM, the certificate template could prefer the Platform Crypto Provider over the standard Windows software provider. If a certificate is configured as not able to be exported, the private key for the certificate is restricted and cannot be exported from the TPM. If the certificate requires a PIN, the PIN gains the TPMs dictionary attack protection automatically.