A first server , comprising: a processor and a memory communicatively connected to the processor, the processor configured to: generate an announcement message including a link specifying a file location and a file name of a user file stored on the first server for a user; wherein the link is configured for encoding a property of the user, which refers to personal identification information of the user; and the link having at least one characteristic that indicates that the link is to be forwarded a second server , since the link is associated with a file transfer process to be invoked, such that the second server retrieves said user file from said first server; propagate the announcement message for delivery to a user device (1301 ... 130N) of the user, so that the user device, based on the characteristic of the link, propagates the link toward the second server ; receive, from the second server , a request to establish a secure connection between the first server and the second server; receive, from the second server , a request for the user file stored on the first server for the user, wherein the request includes the link; and based on receipt of the request for the user file from the second server , identify the user file as being protected by a challenge-response authentication process; propagate, toward the second server, a challenge comprising a request for a challenge value; receive, from the second server, a challenge response including the challenge value; wherein the challenge value associated with the user file comprises the property of the user; determine a comparison value associated with the user file; wherein the comparison value associated with the user file comprises the property of the user;and propagate the requested user file toward the second server via the secure connection based on a determination that the challenge value and the comparison value match. generate an announcement message including a link specifying a file location and a file name of a user file stored on the first server for a user; wherein the link is configured for encoding a property of the user, which refers to personal identification information of the user; and the link having at least one characteristic that indicates that the link is to be forwarded a second server , since the link is associated with a file transfer process to be invoked, such that the second server retrieves said user file from said first server; propagate the announcement message for delivery to a user device (1301 ... 130N) of the user, so that the user device, based on the characteristic of the link, propagates the link toward the second server ; receive, from the second server , a request to establish a secure connection between the first server and the second server; receive, from the second server , a request for the user file stored on the first server for the user, wherein the request includes the link; and based on receipt of the request for the user file from the second server , identify the user file as being protected by a challenge-response authentication process; propagate, toward the second server, a challenge comprising a request for a challenge value; receive, from the second server, a challenge response including the challenge value; wherein the challenge value associated with the user file comprises the property of the user; determine a comparison value associated with the user file; wherein the comparison value associated with the user file comprises the property of the user;and propagate the requested user file toward the second server via the secure connection based on a determination that the challenge value and the comparison value match. <EOS>