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Transport Layer Security pre-shared key ciphersuites (TLS-PSK) is a set of cryptographic protocols that provide secure communication based on pre-shared keys (PSKs). These pre-shared keys are symmetric keys shared in advance among the communicating parties. There are several ciphersuites: The first set of ciphersuites uses only symmetric key operations for authentication. The second set uses a Diffie-Hellman key exchange authenticated with a pre-shared key. The third set combines public key authentication of the server with pre-shared key authentication of the client. Usually, Transport Layer Security (TLS) uses public key certificates or Kerberos for authentication. TLS-PSK uses symmetric keys, shared in advance among the communicating parties, to establish a TLS connection. There are several reasons to use PSKs: * Using pre-shared keys can, depending on the ciphersuite, avoid the need for public key operations. This is useful if TLS is used in performance-constrained environments with limited CPU power. * Pre-shared keys may be more convenient from a key management point of view. For instance, in closed environments where the connections are mostly configured manually in advance, it may be easier to configure a PSK than to use certificates. Another case is when the parties already have a mechanism for setting up a shared secret key, and that mechanism could be used to “bootstrap” a key for authenticating a TLS connection. ==Standards== * RFC 4279: "Pre-Shared Key Ciphersuites for Transport Layer Security (TLS)". * RFC 4785: "Pre-Shared Key (PSK) Ciphersuites with NULL Encryption for Transport Layer Security (TLS)". * RFC 5487: "Pre-Shared Key Cipher Suites for TLS with SHA-256/384 and AES Galois Counter Mode". * RFC 5489: "ECDHE_PSK Cipher Suites for Transport Layer Security (TLS)". 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「TLS-PSK」の詳細全文を読む スポンサード リンク
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