| CPC H04L 67/1074 (2013.01) | 20 Claims |

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1. A data transmission method, comprising:
sending, by a first device, first information of a first data block to a second device, wherein the first data block is a data block to be sent by the first device to the second device, and the first information is used to describe an attribute of the first data block;
searching, by the second device based on the first information, a first index for a second data block similar to the first data block, wherein the first index is used to record, by the second device, information about a data block that has been received by the second device from the first device, and the first index includes a correspondence between a storage address and each of a strong fingerprint and a similar fingerprint that are of the received data block;
sending, by the second device, second information of the second data block to the first device, wherein the second data block was previously sent from the first device and received by the second device, and the second information is used to describe an attribute of the second data block;
locally obtaining, by the first device, a reference block based on the second information, wherein the reference block is the same as the second data block;
compressing, by the first device, a difference part of the first data block relative to the reference block to obtain first compressed information;
sending, by the first device, the first compressed information to the second device; and
obtaining, by the second device, the first data block based on the first compressed information and the second data block.
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