01005805 Case File No. 002/19-09-2007/ECCC/TC E313 249. Most, but not all, CPK telegrams were encrypted before transmission.778 Unencrypted messages were sent in Morse code.779 Secret messages were encrypted using a substitution cipher.780 Additional layers of encryption were used for highly confidential messages, such as those pertaining to cadres’ travel plans. 781 Special code numbers were also used to refer to specific individuals, locations and offices.782 250. Telegrams were generally encrypted (or decrypted) and transmitted (or received) by different people.783 Thus, outgoing telegrams were usually prepared in writing and delivered to an ‘encoder’; the encrypted messages were then sent to a separate telegraph operator for transmission.784 At the other end, the encrypted messages were received and transcribed by another telegraph operator, before being taken to a ‘decoder’ for decryption.785 The decrypted messages were then delivered by messenger to the final recipients.786 Witness NORNG Sophang, who ran the telegram encryption and decryption unit at Sothearos School from 1975 onwards, 787 confirmed that this separation of responsibilities was intended to “preserve the principle of secrecy” within the CPK.788 778 T. 14 December 2012 (PHAN Van), p. 12; T. 29 August 2012 (NORNG Sophang), p. 64; T. 3 September 2012 (NORNG Sophang), p. 25. 779 T. 29 August 2012 (NORNG Sophang), p. 64; T. 17 December 2012 (SUON Kanil), pp. 51-52. 780 T. 3 September 2012 (NORNG Sophang), pp. 20-22 (describing the use of a “table of 100 squares” to encrypt text); Attachment to NORNG Sophang Interview Record, E3/1732, undated; T. 11 December 2012 (PHAN Van), p. 101 (referring to a “10-digit coding” system); KUNG Sokha Interview Record, E3/465, 21 January 2008, p. 5, ERN (En) 00204757. 781 T. 3 September 2012 (NORNG Sophang), pp. 24-25;T. 11 December 2012 (PHAN Van), p. 101. 782 KHAM Phan Interview Record, E3/57, 10 March 2009, p. 4, ERN (En) 00290506.See e.g. T. 3 September 2012 (NORNG Sophang), p. 83 (stating that “47” was a code number for SON Sen); T. 28 March 2012 (KAING Guek Eav), p. 87 (stating that “89” and “62” were code numbers for SON Sen); SUON Kanil Interview Record, E3/344, 18 August 2009, p. 9, ERN (En) 00384430 (stating that “18”, “25” and “35” were code numbers for KE Pauk). See also, Section 5: Administrative Structures. 783 T. 11 December 2012 (PHAN Van), p. 101; T. 17 December 2012 (SUON Kanil), p. 51. 784 T. 7 June 2012 (SAO Sarun), pp. 16-17; T. 29 August 2012 (NORNG Sophang), p. 39; KUNG Sokha Interview Record, E3/465, 21 January 2008, p. 6, ERN (En) 00204758. 785 T. 11 December 2012 (PHAN Van), p. 101; T. 14 December 2012 (SUON Kanil), pp. 81-82; T. 29 August 2012 (NORNG Sophang), p. 39; KUNG Sokha Interview Record, E3/465, 21 January 2008, p. 6, ERN (En) 00204758; PON Ol Interview Record, E3/373, 7 May 2009, pp. 4-5, ERN (En) 0033652700336528. 786 T. 13 June 2012 (OEUN Tan), pp. 63-64; T. 29 August 2012 (NORNG Sophang), p. 39. 787 T. 6 September 2012 (NORNG Sophang), p. 83; T. 29 August 2012 (NORNG Sophang), p. 55. 788 T. 6 September 2012 (NORNG Sophang), pp. 64-65. Case 002/01, Judgement, 7 August 2014 - Public 138