A method for authorising a second client to a server for a user account in order to establish a secure link between the second client and a first client, wherein the method comprises the following steps: a) generating a random number by the first client, b) displaying the random number by the first client, c) generating a first hash value (Hash1) from the random number by the first client, wherein the first hash value (Hash1) comprises a symmetric key (Ktan), a password and an initialisation vector, d) generating, by the first client, a first data packet (Token1) from a name of the user account, from a first public key of the first client, and from a hash value of the first public key, e) encrypting the first data packet (Token1) by means of the symmetric key (Ktan) and the initialisation vector by the first client, f) generating a second hash value (HPWC1) from the password with use of the initialisation vector as salt by the first client, g) transmitting the encrypted first data packet (CToken1) and the second hash value (HPWC1) from the first client to the server, h) receiving, by a second client, the name of the user account and the random number from an input means of the second client, i) generating the first hash value (Hash1) from the random number received via input means by the second client, wherein the first hash value (Hash1) comprises the symmetric key (Ktan), the password and the initialisation vector, j) generating the second hash value (HPWC2) from the password with use of the initialisation vector as salt by the second client, k) transmitting the second hash value (HPWC2) from the second client to the server, l) comparing the second hash value (HPWC1) obtained from the first client with the second hash value (HPWC2) obtained from the second client by the sever and, in the event of a match, transmitting the encrypted first data packet (CToken1) through the server to the second client, m) decrypting the encrypted first data packet (CToken1) by means of the symmetric key (Ktan) and the initialisation vector by the second client to obtain a decrypted name of the user account, a decrypted second public key, and a decrypted hash value of the second public key, n) comparing, by the second client, the decrypted name of the user account with the name of the user account received via input means, the decrypted public key with the first public key of the first client, and/or the decrypted hash value with the hash value of the first public key of the first client. a) generating a random number by the first client, b) displaying the random number by the first client, c) generating a first hash value (Hash1) from the random number by the first client, wherein the first hash value (Hash1) comprises a symmetric key (Ktan), a password and an initialisation vector, d) generating, by the first client, a first data packet (Token1) from a name of the user account, from a first public key of the first client, and from a hash value of the first public key, e) encrypting the first data packet (Token1) by means of the symmetric key (Ktan) and the initialisation vector by the first client, f) generating a second hash value (HPWC1) from the password with use of the initialisation vector as salt by the first client, g) transmitting the encrypted first data packet (CToken1) and the second hash value (HPWC1) from the first client to the server, h) receiving, by a second client, the name of the user account and the random number from an input means of the second client, i) generating the first hash value (Hash1) from the random number received via input means by the second client, wherein the first hash value (Hash1) comprises the symmetric key (Ktan), the password and the initialisation vector, j) generating the second hash value (HPWC2) from the password with use of the initialisation vector as salt by the second client, k) transmitting the second hash value (HPWC2) from the second client to the server, l) comparing the second hash value (HPWC1) obtained from the first client with the second hash value (HPWC2) obtained from the second client by the sever and, in the event of a match, transmitting the encrypted first data packet (CToken1) through the server to the second client, m) decrypting the encrypted first data packet (CToken1) by means of the symmetric key (Ktan) and the initialisation vector by the second client to obtain a decrypted name of the user account, a decrypted second public key, and a decrypted hash value of the second public key, n) comparing, by the second client, the decrypted name of the user account with the name of the user account received via input means, the decrypted public key with the first public key of the first client, and/or the decrypted hash value with the hash value of the first public key of the first client.