PKCS # 1 : RSA Encryption Standard

This standard describes a method for encrypting data using the RSA public-key cryp-tosystem [1]. Its intended use is in the construction of digital signatures and digital envelopes , as described in PKCS #7 [2]: • For digital signatures, the content to be signed is first reduced to a message digest with a message-digest algorithm (such as MD5 [3]), and then an octet string containing the message digest is encrypted with the RSA private key of the signer of the content. The content and the encrypted message digest are represented together according to the syntax in PKCS #7 to yield a digital signature. This application is compatible with Privacy-Enhanced Mail methods [4,5]. • For digital envelopes, the content to be enveloped is first encrypted under a content-encryption key with a content-encryption algorithm (such as DES [6]), and then the content-encryption key is encrypted with the RSA public key(s) of the recipient(s) of the content. The encrypted content and the encrypted content-encryption key are represented together according to the syntax in PKCS #7 to yield a digital envelope. This application is also compatible with Privacy-Enhanced Mail methods. The standard also describes a syntax for RSA public keys and private keys. The public-key syntax would be used in certificates; the private-key syntax would be used typically in encrypted private keys [7]. The public-key syntax is identical to that in both X.509 [8] 1 Versions 1.0–1.3 are superseded by this version. The earlier versions were distributed to participants in RSA Data Security, Inc.'s Public-Key Cryptography Standards meetings in February and March 1991.