The use of radix 64 expands a messa

The use of radix 64 expands a message by 33%. Fortunately, the session key and signature portions of the message are relatively compact, and the plaintext mes-sage has been compressed. In fact, the compression should be more than enough to compensate for the radix-64 expansion. For example, [HELD96] reports an average compression ratio of about 2.0 using ZIP. If we ignore the relatively small signature and key components, the typical overall effect of compression and expansion of a file of length X would be 1.33 * 0.5 * X = 0.665 * X. Thus, there is still an overall compression of about one-third.

One noteworthy aspect of the radix-64 algorithm is that it blindly converts the input stream to radix-64 format regardless of content, even if the input happens to be ASCII text. Thus, if a message is signed but not encrypted and the conversion is applied to the entire block, the output will be unreadable to the casual observer, which provides a certain level of confidentiality. As an option, PGP can be config-ured to convert to radix-64 format only the signature portion of signed plaintext messages. This enables the human recipient to read the message without using PGP. PGP would still have to be used to verify the signature.

Figure 18.2 shows the relationship among the four services so far discussed. On transmission (if it is required), a signature is generated using a hash code of the uncompressed plaintext. Then the plaintext (plus signature if present) is com-pressed. Next, if confidentiality is required, the block (compressed plaintext or com-pressed signature plus plaintext) is encrypted and prepended with the public-key-encrypted symmetric encryption key. Finally, the entire block is converted to radix-64 format.

On reception, the incoming block is first converted back from radix-64 format to binary. Then, if the message is encrypted, the recipient recovers the session key and decrypts the message. The resulting block is then decompressed. If the message is signed, the recipient recovers the transmitted hash code and compares it to its own calculation of the hash code.

Kết quả (Việt) 1:

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Kết quả (Việt) 2:

Failed to use the basic parameter 64 extend a message via 33%. Có thể người đàn ông change, the key versions and signature of the person was reported that relative minor Gòn, known and mes-Hiền Triết have been compressed. Trọng perform te, compressed should be more đủ for compensation đạp cho that extend Basic zero-64. For example, [HELD96] reports an Ti Lệ compressed average between 2.0 use of ZIP. If we leave through components signature and quan important relative minor, effectiveness count be dictionaries screen of compressed and expansion of one file length of X will be 1.33 * 0,5 * X = 0665 * X. Since the Vây, still be a compressed count be of between the one ba. One khía Cảnh Đáng Note of the algorithm Basic zero-64 as it is one way Mu Quảng converted lines input for Radix-64 formatted any ke nội dung, even if the first to the would happen be văn bản ASCII. Since the Vây, if you one messages are signed the but not be ciphertext and change not apply to all block, work quality to be read for the observation regular, provide a level degrees first format kept secret. Như an option, PGP be config-ured to change to the form Radix-64 only the signature of messages known journal. This is allowed recipients con people to read messages which is used used PGP. PGP still would be used for verification Minh signature. Hinh 18.2 cho find new quan the system center phần tư services until sự do dự thảo Luận. On the traditional (if necessary), one signature been created equal to ra usage one has hash of bản known can compressed. After that, bản known (plus with the signature if) be com-EP. Tiếp in, if it is a secure is required, block (bản known or com-EP signature compressed plus with the plaintext) being ciphertext and add to your Phia first for the key ciphertext arguments Xung key public khai ciphertext. final, all volume to be converted to Radix-64 format. Ngày tiếp got, volume up to once the first to be converted return from DB format 64 hát that Nhi. After that, if you messages are ciphertext, recipients suppress the key versions and decoding messages. blocks the result is a then extract. If not notify the journal, recipients suppress encryption hash traditional and compare it is with the machine operator own your of encrypted hash.